The MK 25/X650 is one of SP's top of the line regs. If you're doing recreational dives, you don't need such a high performance reg. Not that it's bad to have one, but if you want to save some money, you could get the G250 2nd stage and you'd be every bit as happy with it. You could also save some money getting the MK17 1st stage, or even the MK16 if you can find one on close out.
For single tank recreational diving, not any deeper than 130ft, the workhorse MK2/ R190 would save you ALOT of money and perform very well. Don't listen to anyone who tells you the unbalanced piston 1st stage will breathe poorly at low tank pressures; the truth is it will deliver plenty of air easily until your tank gets really low, like 300PSI. If you're at any depth at that tank pressure, it's really time to head for the surface...as a new diver this can be a blessing if you forget to monitor your SPG and find yourself unexpectedly low on air. A high performance balanced piston, like the MK 25, will breathe essentially the same right down to the last breath, and finding out you have NO air at depth could be a very dangerous situation. It's unlikely to matter as long as you keep checking the SPG.
These are just SP regs. There will be many opinions on other brands. Any reputable company, aqualung, apeks, etc will work really well, and most have lifetime warranties, so you might check out what's easily available and serviced in your area. Good luck!