Yea, I have been working on a DSP project. Someone suggested making it a DIY, and it could be. The issue is that it is all SMT, fine-pitched (0.5mm lead pitch), which is a bear to solder even if you're used to doing it. Also, a 4-layer board which is needed for a reliable 120 MHz bus is beyond all but the most seasoned DIY etchers out there. A 'kit' is an option but I'm not so sure that you couldn't buy a PCM81 or 91 for the price of a box, pre-stuffed PC boards, transformers, jacks, etc.
There is a possible DIY reverb is using the Wavefront AL3201 chip. It's still all SMT but the narrowest pitch is 1.27mm - you can even DIY-etch a board like that. I don't use the original 'Picoverb' preset algorithms - I load in my own software in there, and I use the loop Lexicon-style algorithms.
For interest's sake, I'm using a MCF51AC256 host controller (the user interface and all of the presets live here), a DSPB56366, and the prototypes have 512k by 24 bits of 10ns SRAM - the next revision will have double that. I wanted to use cheaper DRAM but getting EDO RAM is exceedingly difficult. You don't need more than maybe 64k or so to do a convincing reverb, I'm equipping this to do multiple digital delays. The RAM costs almost $60, and the DSP is about $20. DRAM would have been about $5.00 but most DSP's don't have SDRAM controllers.
-Dale