I have a couple questions for you guys:

1. Are the JCM800 combos as good as the head + cabs?
2. What's the difference between the 2203 and 2204? Is the 2203 100 watts and the 2204 50 watts?

The difference between the combo and the head is limited only to the cabinet design and stock speakers in the combo. Regarding the electrical side of things, all is the same, but of course they'll never sound the same as you'll never find a cab with the exact same properties/dimensions as the combo.

I'm no expert on the technical details of the 800's, but if I recall correctly the major differences between the 2203 and 2204 were the output transformer and the number of power tubes.
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Yep. You certainly would. The only time there would be a real difference, I guess, is if speakers and valve types were different. Take the Marshall JCM2000 DSL401 combo and DSL50 head. I think their power amp valves are different, so they'd have a different tone. I've only played the DSL401, though, so I can't say for certain how different it would be.
Just quick FYI:

You won't get the tone you desire unless you crank it--so don't be dissapointed when you first plug in.
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Yeah that's another thing I'm considering right now. It's kinda between those, AC30, and a lot of other stuff. I'm probably gonna jump on whatever pops up.
Also, don't forget that 50-100W combos are heavy as ****.
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