As to sound characteristics of the four brands noted, my general impression is that McIntosh would tend to lean a bit warm, ARC the most neutral, and Musical Fidelity and Bryston would tend to lean a bit bright.
As to features, if you want both a headphone jack and phono stage, then McIntosh or Bryston offer really good candidates. These are both excellent brands which hold their value as well as any and getting service when needed should not be an problem.
On the other hand, if you need the phono stage but can do without the headphone jack, then the Musical Fidelity M6PRE/M6PRE separates would be worth considering. They are what I use and they pack a lot of value for the money; however, MF may not hold its value quite as well as the others and some have reported problems getting service on MF products.
If you don't need either the headphone jack or the phono stage, then I'd put ARC at the top of your list along with Bryston (I assume you'd be looking at the b135 sst2 where I think headphone and phono are options that you can take or leave).
If you need headphone but don't care about phono, Bryston looks like the best option to me. A 20 year warranty is pretty hard to overlook!
