I currently have a Zeagle FlatHead 7 LT, with the 2nd that comes with it and a very cheap Octo (costed like $60) the zeagle 2nd stage is a bit scrashed and it works perfectly but im a bit worry about my octo so i was thinking that instead of replacing my octo with another one, why dont i just get a better 2nd for me and use the zeagle as an octo...
The second stage that comes with the Flathead is / should be a Zeagle Z, which is a high end, lightweight, user-adjustable (venturi control and breathing resistance control) second stage. For many years, the high end Zeagle 2nd stage was the ZX, which is equivalent to the Z in almost everything except size - the Z is more compact than the ZX - and weight (the Z is substantially lighter than the ZX). You would be hard-pressed to find a discernibly 'better' second than the Z (at least in terms of objective breathing performance and user adjustability), although you can certainly find a number of 'just as good' seconds. So, the idea of 'looking for something that's 'better' does not seem particularly compelling, at least to me. Having said that, is there anything you don't like about your primary second stage? You may decide to get a different primary second stage because of size, or weight, or the 'feel' of the breathing control knob, for that matter. That doesn't make another second stage 'better' in terms of performance, but may mean it is better suited to you, in terms of your comfort with it. Out of curiosity, when you refer to a 'very cheap Octo', presumably - since you mention it - you are referring to the price. What brand / model octo is it? Did it come with the Flathead, and did the seller add it in at cost to make the deal? If that is the case, it may or may not be 'cheap' in terms of quality or performance.
Does the 2nd stage make any difference? and if it does what should i look for whats better 2nd than what i have now?
The absolute answer to the question as posed is, 'Yes, the second stage makes a difference.' However, high end second stages across manufacturers generally perform quite well, and it is difficult to discern objective differences in performance. High end second stages are generally going to have a venturi control, and generally will have some user adjustability in ease of breathing, whether the manufacturer calls it 'cracking pressure control' or 'user-adjustable breathability', the functions are the same. However, there may be differences in materials, there may be differences in size and weight, there may be differences in the size of the exhaust tee, etc. Most of these do not relate to breathing performance at all, rather to user preference.
Durability is often as much a function of owner usage as it is of quality. I have two Zeagle ZX second stages that I have used for 12 years, serviced peridically, and they perform exceptionally well. Scratches on the face, and the housing, and the exhaust tee, etc., are entirely cosmetic. I also have two other ZX second stages for which I have had to replace the housing - but not because of any quality issue, rather because of bozos on boats mishandling their gear. I don't consider that an indicator of poor durability, and both second stage housings were easy and inexpensive to replace.
Threads like this usually bring out the subjective preferences of posters for whatever they happen to use. You can find people on SB who fervently (aka rabidly) favor some particular brand, be it Zeagle, HOG, Apeks, Scubapro, Mares, Atomic, whatever (the list is long) and who will say that whatever brand they favor is clearly better. What that actually boils down to is usually personal preference, and like others I have a number of my own.
Personally, I like to use identical primary and alternate second stages on my recreational regs, for a variety of reasons including simplicity of servicing (kits and tools), equivalent performance in case the octo is needed in an emergency, etc. Personally, I have no trouble mixing brands - pairing a Zeagle 50D first stage with an Apeks ATX200 second stage, or a Zeagle ZX second stage with a HOG first stage, or two Mares second stages with a Zeagle DS-V first stage. The combinations all work just fine - for me. Personally, I like a smaller exhaust tee, and the smaller one (of two) that came with my Apeks XTX50s suits me just fine. Personally, I subjectively think my ATX 200 second stages breath better than my Zeagle ZX second stages, or even my Apeks XTX50 second stages, but I suspect that any objective differences would be tough to quantify. And, personally, I really don't like the mouthpieces that come with Zeagle regs at all (and have changed all my second stages, irrespective of brand, to Apeks Comfo-Bites). That doesn't mean there is anything wrong with the Zeagle second stage itself, however.
I wouldn't go out and buy a different primary second stage, just because someone here (me or anyone else) says it is the best on the market, or is clearly better than the Zeagle. Instead, evaluate what you like and don't like (if there is anything you don't particularly like) about your primary, and about your octo for that matter (other than it was simply inexpensive), and act on the basis of that assessment.
.... And Why would anyone want the back-up regulator to be anything but at least equal to the main 2nd stage 
