Well, this is both the resolution for the project and the measurement of the energy resolution (pun intended?).

I've taken some rough measurements, just so as to see the general ballpark i'm in regarding energy resolution.

For 226 Radium from a "choob" (Tube) meant for Radars, i got about 9.4 % FWHM (Full Width at Half Maximum) which is pretty close to the 8% a regular Sodium Iodide crystal has. Granted, they're usually spec'd for 8% FWHM 662keV, but i've still got some noise in the cables and too much digital gain. Amplifier PCBs are here, but i'm still waiting for parts.

What i was expecting

What I got 

There's a lot of background and XRF, but the peaks are where they should be and, with some copper shielding and a lead castle I'll get better results.

For now, I'm quite pleased with the result.