I've been researching gas dryers for about 8 months now, and we run an Advance/American Tex-Air 48" gas/electric combo dryer that will probably cure more shirts per hour than any new dryer with the same size belt and heat chamber. Our 48" can handle 2 autos since the belt speed is so fast and if we loaded both autos from the side of the belt instead of the end like we do with one auto, it would be fine and likely not have to be real creative when folding the shirts onto the belt. Running the auto at 500-600 per hour, we can put the shirts on the belt completely layed out flat, not folded. Now when we get up to 1000/hr, we have to fold the shirt to where only the image area is showing.
I'm with most of the guys when suggesting AT LEAST 10' heat chamber if you're going to be doing discharge/WB and 2 autos, and I'd try real hard at getting a 60" belt, 12' heat, at least 5' infeed and at least 5' outfeed.
Now as far as the brands go, if you could find an american texair like ours, newer of course that was gas with electric radiant panels as well, it would be a steal. I've seen quite a few of these on the used market and they go for nothing, yet ours runs without fail every single day and has had millions of shirts fed through it in it's 20+ year history. I know if we tried to sell ours, nobody would pay what it's really worth to our shop, or what it would be worth to the shop buying it. It runs all day, every day yet it's essentially worthless on the used market even though it's value to us is second to nothing in our shop. It's weird that it works like that with dryers, but ours is a beast that still outperforms most new dryers when it comes to the amount of shirts it can cure.
I've heard great things about Interchange and M&R, and that's about it for good reviews on the dryer market. The other major dryer manufacturers have been hammered by those I talk to about them, and there seems to be nothing good to say about them unfortunately. So there are some stinkers out there in the dryer market, but I can say that there are at least 3 that will serve you well.