Glad that you are digging the iAMP 800, Phil! I told you that once you heard EA gear, you'd be hooked!
D, you seem to be committed to the iAMP 800, and I have to agree that it is an excellent choice (with the Walter Woods Ultra being another, albeit more expensive, option to consider).
With regard to the CXL-112, I do think that it would work well with the iAMP 800. In fact, I think that the two are somewhat made for each other, as I think that the CXL-112
needs the extra thickness that the iAMP provides (relative to some other solid state heads). However, as good as the CXL-112 is, there are other EA cabs that I prefer. I love VL-208's, and as Uncletoad points out, the iAMP 800 with two VL-208's is a phenomenal double bass rig. I agree with my amphibious friend that two VL-208's, alone, don't quite get it for "electric bass" (I'm not a "Fender guy"

), but three VL-208's is an entirely different story!

The transition in sound from two to three VL-208's is astounding. I'm still trying to find a 4th, but three VL-208's and a VL-110 make for a close approximation, and these four cabs make for a mighty, modular, "mini" rig. Oh, and with its 2 ohm stable capabilities, the iAMP 800 will eat this up!
Other great EA cab recommendations would be virtually anything from the VL-series line. VL-110's are excellent, though not as good as VL-208's for upright (or for midrange in general). VL-210's are the absolute bomb when you give them enough power and push them hard (I mean really hard). They shine like nothing else I have tried in this regard. However, at lower volumes, VL-208's will sound much more articulate and well-balanced. The CX-310 (or VL-310, which is the same cab) will give you very nearly everything that two VL-210's will offer, but with even more high end clarity (which you can dial out, if you don't like). They are a beast to lug around, but if you have a big old van, don't have to go up and down steps, and are used to hauling SVT fridges, then it probably wouldn't seem too bad.

I just picked up a VL-108, and it is an incredible cab for its size, but it has volume limitations, of course.
I recently picked up a CXL-112 and a CXL-210. Of the two, if I had to only play through one, I'd prefer the CXL-210. It's a bit more full and balanced sounding, to my ears. The two are great together. I'd imagine that the NL-210 sounds stellar, though I haven't heard one. Mike Dimin likes both a CXL-112 and NL-210 together. If it were me, and these were the only two that you were considering, I'd get the NL-210 first, then the CXL-112.
Now, another path to consider, especially in your 22-piece big band (where you probably aren't going to be punishing the floorboards quite to the extent that Uncletoad does!), is a pair of Wizzy's. I have had one for a while, and it is truly the most impressive sound out of such a small, light cab that I have heard. Last night, I had the opportunity to try it with a second Wizzy, and the results are astouding. The Wizzy is not a good cab for subterranean lows, but it is a very full, warmish sounding cab, that somehow retains excellent clarity and balance. There are no tweeters on the Wizzy (so no sparkly highs), but it has good high end clarity and definition with its wizzer cone. I would that an iAMP 800 and two Wizzy's would be ideal for a big band situation. Of course, the iAMP 800 with a CXL-112 and NL-210 would be even more formidable (though more expensive).
Hope this helps, Tom.