The JCM800 has no loop.
Wizard - Vintage and modern sounding amps based on Marshall's made by the AC/DC guitar tech,
Friedman - Makes the 'Naked' and 'Browneye' (formerly Marsha) Amps. He makes all kind of high spec gear
Voodoo Mods - a company specialising in mods. you cannot 'try before you buy' so its a risk sending an amp to these guys, and shipping to a from Greece to the US to get an amp modded will be expensive.
Naked amp looks like a 2 channel Marshall style thing. Nice though. follow Tekbow's link.
The 'Browneye' in a single channel amp with various switching to increase gain and change voicing. I THINK it includes switchable diode clipping, which is similar to the 'jose' or 'cameron' mod. (if im wrong I hope someone will correct me)
The Splawn fits in here. The quick rod is 2 channel but the gain channel has the 'gears' feature. which is switchable boosts at different points in the preamp. It will probably do everything your after + give you a clean channel.
SLO100 - way too expensive. But if you don't need a clean channel but you want an FX loop, the Hot Rod Avenger might be the right way to go?! basically an Avenger with an FX loop. That would be right up your street. also
Peavey 5150 - Loads of gain, has a loop. Probably going a hiss a lot compared to the Splawn or Soldano. But (and i liked this) if you use the 'Low' input and run the preamp gain kind of high, I think it sounds better and you'll be able to use the volume knob to roll off distortion better. The clean channel in the 5150 isn't that good. and its not that good in a 5150 MKII either. Never played a MKIII
DSL - Probably OK. I've used one once but I think other amps in this list are perhaps better. I don'y have much experience with this amp but it's a popular one.
If you don't care about cleans and you want a really good stripped down, simple amp with plenty of gain on tap and an FX loop. I think forget the SLO and go with an Avenger with FX Loop (hot rod avenger).
If you think you might want flexibility in future, go for the Splawn.
If you want to save some cash i'd go for the 5150 before the DSL.
Forget the JCM 800 2203. No Loop.
EDIT:
The marshall site says the current 'vintage series' JCM 800 2203 DOES have an series fx loop. If thats the case I'd say it would be better than the DSL, but it has less perceived gain. I don't think original JCM800 2203's have FX loops though. so if you get one second hand, best to check it out.