Quick answer, ignore the QTX. I actually have some, and they're fine, as long as you respect their limits. Theoretically, mine are the top of the range ones, so cheaper ones should have lower specs.
Don't touch the Ekho with someone else's bargepole.
The Soundlab ones aren't likely to be fab, nor the NJS.
The RCF are the class of that list, but as 322s they might be a touch harsh close up, as apparently the throat on them is 2", and designed for long throw. 312s might suit you better.
The Db I can't tell you much about, though they're a pretty well respected brand.
Now the LD, well I have the higher spec 12" version, and love them to bits. The GT are the cheaper ones, but still good cabs. I've been considering the ones you're looking at myself.
However, have a look around for Proel V15a. I've used them, and they're very very good. They may still be over budget, but well worth a look.
The golden rule though, if at all possible:
Listen before you buy.
Edit: Re Toby's post. 310s are very good, but I'd go for 312s, given the choice. They'll cope without a sub(s)
The Yamaha are very good, no question.
The older Mackie/Tapco Thumps ,well
look here