I'd say the next step after a CMOY is maybe a Gamma-1 or Gamma-2, which will teach you how to make do SMD (surface mount) soldering. I'm not sure what a Buffalo 32 entails, but my guess is it would involve more case work than a Gamma-1 or 2. Those DACs allow for the capability of buying pre-drilled panels from AMB, which helps tremendously if you have no case work skills. You can drill your own panels though because there are so many options with AMBs DACs. The next step as far as amps goes is probably a CTH (which I'm doing a group buy for the pcbs right now -- so get in while the getting is good) or a CK²III, which I hear is really nice amp that is fairly easy to build and requires some minor case work. The next step is an M³, which is a little harder and requires a separate power supply. The B22 is after that and is probably somewhere around the difficulty of a M³. Some amp pcbs have SMD, some don't. The hardest part to DIY is on your wallet and then comes case work skills, which require the proper tools to do a sufficient job. I'm at the point where I could do the more high end boards, but don't have the case work tools and know how. Like I said before -- I'd do the Apheared 47 first then move up to a decent amp and DAC then up to the Buffalo 32 and then a B22.
All you need for the low end amps is an altoids can, a nice hole punch from staples, and a round file to make the holes bigger. Buy jacks that are plastic and not metal because it's better that everything is isolated from the metal can. Trust me... I learned this from my recent DC powered Apheared 47 build. If you use a 9V battery isolation is less necessary.