First off, there is no best- just what may be best for a specific situation. The Avalon M5 is nice, sweet sounding preamp. The Focusrite 220 is a very good preamp, compressor and eq. Anything made by TL audio has dissapointed me and my standards. The Summit cheaper stuff is not up to par with their professional products. If your shy of having good eq or compressor channels, the Focusrite 220 may be a better tool for you to buy at his time.

I'm with AudioGaff on this one. The ISA 220 would be the best sounding of the bunch in terms of flexibility. It would work best on the widest variety of sources. It would also be the best investment returning to you the price should you decide to sell it later.

I personally do not get that excited with Avalon's stuff, it is a bit too purest / clean sounding and the less expensive Summit gear is simply scaled down designs intended to meet a price point. TLA gear is more of a hybrid design and not a true valve design and my opinion of that is a good solid state design shouldn't need a tube stuck in there to help it out. I prefer tubes to be tubes and solid state to remain all solid state.