Its meaningless to say that desktops are definitely better than portables, as illustrated by dusty. However, blackgates aren't cheap, and so far I haven't seen anything that violates the pattern that desktops have better price/performance ratios to portables.
Again no. However, portables are usually a compromise in design, simply because you can't have the kind of power and space avaliable to desktop setups, not to mention heat dissipation capabilities. Thus I don't really expect to see class A amplification in portables, or your pocket would be smokin.
Whether to get portables or not is a matter of need. If you need it portable, then you really have no choice. But if you don't need portability, then if I were you I'll stick to desktop setups.
I don't think it matters, but then I don't own any real powerful equipment to be able to make that statement authouratively. But frankly even if it DID matter, your amp budget at 2-300 bucks would probably not give any discernable differences.
My 2 cents worth. I'm new here, so I stand to be corrected.
Arthur.