Sorry for the long reply, but the more I feel like blasting out on all the
OT folks, the more I realize I should just keep on topic, or as closely connected to amps as effects can be
Say, what's your application? Live? Practice only? Studio? all? This makes a big difference - It sounds like you're talking about solo-bedroom-jamming

, but correct me if I'm wrong...
I've tried the GT-5, the predecessor, and can vouch that that one is a great unit, if a digi multi floor-based box is what you going for. My buddy who owns it is a little overwhelmed by it, and I keep recommending he trade it in for the GT-6, which looks a lot easier to use. I've been intriqued by the GT6 unit myself - anything with a SPDIF output and speaker sims gets me reved as I like running the amp's DIs into them for recording.
Boss has a new unit (GS-10?) This looks really intriguing if you're doing any basement studio stuff and built in little speakers - great for working out stuff on the back porch with an acoustic player! It'even more expensive though, and it has no pedal board - it's basically a GT-6 with a mic pre, and USB for recording to PC.
If you're having trouble motivating yourself, recording some of your songs and overdubbing on top of them can be a real rut-buster I find - so this box might be worth the extra bux for you, so long as you've got a PC....
I've got a Yamaha DG-stomp, which I liked a lot until it conked out - I've got to open it up and see if any of the chips are lose or if I can find a cracked trace... but it seemed really tough for a year or two, and it's incredibly easy to use. It's probably the best for doubling as a desktop processor and a floor based processor. You can prolly find them even *new* at GC for $150, as they're discontinued. There is no stomp box modeling, and no loop, but there is the SPDIF out... Anyway, it's the most dynamic and realistic sounding amp-in-box machine I've heard.
I also recently picked up a J-station for $60 when the DG conked out...
it's a nice box - all metal... Totally not suitable for stage unless you buy an outboard midi board... it does 1 modulation at a time, plus delay and reverb. Again, there is no stomp box modeling, and no loop, but it also has a digital out. It's a surprisingly good sounding unit, after my bad experiences with some other Digitech gear (2120, rp-12).
I'd recommend going to the biggest store you can, and try everything out, even if it's a really long drive for you. Try to forget about how pretty or ugly a box is! Even better if you can find a place with lots of used gear, as it's priced more reasonably than all the new junk... After all this, I'd just hit ebay, or at least check it...
Just remember that the $400 you spend now will only get you $150 two years from now...