I like Apeks and have XTX50s, an XTX100 (which I bought 2nd hand here on SB for a reasonable price) and an XTX200. Most of my dive buddies have them and the shop where I dive most is an Apeks dealer so they suit me (YMMV depending on where you plan to dive)
Having said that, SP are common and therefore cheaper/easier to find 2nd hand, and pretty easy to find service/parts for, so I would agree with the other posters, mk17/mk25 with S600+ second stage & octo
Alternatively the HOG regs have been geting some good reviews (I also have a D1 cold set although I'm about to sell it to a buddy, but not because I don't like it) and are competitively priced
$400, including first stage, second, octo, hoses and SPG, should cover new HOGs (if you get a good deal) or 2nd hand Apeks or SP
Having said that, SP are common and therefore cheaper/easier to find 2nd hand, and pretty easy to find service/parts for, so I would agree with the other posters, mk17/mk25 with S600+ second stage & octo
Alternatively the HOG regs have been geting some good reviews (I also have a D1 cold set although I'm about to sell it to a buddy, but not because I don't like it) and are competitively priced
$400, including first stage, second, octo, hoses and SPG, should cover new HOGs (if you get a good deal) or 2nd hand Apeks or SP