That should be a good choice, and hard to beat for the price. Colt is better, but will be over $1,200 easily out the door for a 6520, and probably in the high $1,300, low $1,400 range for a 6920 out the door.
I'm not a fan of the dissipators. They have a gas block underneath the handguards and the front sight post is just a front sight post, rather than that and a gas block. The only advantage to them is if you're the type of shooter who likes to use a traditional handguard but likes to be able to position their hand further forward. For that, they're perfect.
I'd rather just have the shorter CAR or M4 handguards and add a vertical grip. Don't need to buy a super-duper expensive high end FF rail system costing $350 to do a forward grip. I bought a GG&G rail that bolts through the holes in the bottom of the handguard, and attached a TDI (stubby) grip to that. Works great. I have no idea what people are talking about when they think this method is not sturdy and strong. There's no play in mine even when I pull on it very hard. I put gorilla force on it and have no problems at all. Then again, my Colt handguards are thicker than other AR's I've seen. I wouldn't attempt that method of grip attachment with the flimsy handguards found on some kit-guns. Perhaps that's what people refer to when criticizing this method for grip attachment. Total cost was around $30.
Anyway, my point was, a verticle grip is BETTER at dealing with hot handguards than any dissipator style rifle in my opinion because you avoid the handguards entirely. Even dual-heat shielded M4 handguards become uncomfortably hot if you run the gun hard. I suspect most AR owners never really run their rifle that hot...
So the dissy offers 2 features...the ability to put your hand much further up the guards on a carbine length rifle, and improved handling of heat over standard guards. Some people just like the looks.
Go for it. If you don't have an AR already - you *need* one