I used the US Modular Sleep System for 6 years in a variety of climates and temperature ranges from +47 in Iraq to -40 in Norway.
I prefered it to the Canadian 2-bag down sleeping bag, primarily because if it got wet, it didn't lose its insulation value, it had a built-in hood, and the lightweight patrol bag was pretty light, and quite compact, and when used together, the snap system kept the bags from twisting inside one another, like I found to be an issue with the CF bags, even when tied together.
The 'Patrol' outer bag was great for use in Virginia/North Carolina/California climate zones 3 seasons out of the year, whereas I think the Canadian inner and outer are about the same weight/bulk as one another. The downsides to the bag were its bulk (I believe it uses an older generation of Polarguard, which isn't very compressible) and that over time (we're talking several years) the insulation broke down somewhat and didn't keep me as warm as when it was brand new.
If you can pick a brand new one up from ebay or somewhere else for cheap, then good on you. Buying used is a bit dodgey though, as you can't be sure what condition it's in and how much life the insulation has got left in it.
FWIW, Extreme Outfitters has got the Recon line of sleeping bags, but having handled the bags and finding them comparable to the thickness of a standard US poncho liner, find that the -5 temperature rating is more than a bit 'ambitious', but comfort is very much a relative thing. This is not to say that the bag isn't good, as it'd probably make an excellent alternative to a poncho liner for summer/jungle use, but I certainly wouldn't be using it at -5 and expecting to get any sleep, but rather would be waking up every 10 minutes, shivering and shaking uncontrollably.
If you've got a bit more money to spend, have a look at the Integral Designs bags (http://www.cpgear.com/default.asp?mn=1.19.56&f=bp&pcat=37&p=-1). DHTC/CANSOFCOM have been using these for some time now and given that there's another tender on MERX out for them, don't appear to be too unhappy with their performance.