Hey Drivie, hope you're doing well. I myself have four Heavy barrel CAR's. However, am getting an M4 profile upper from Rock River in the next few weeks. I like the HBAR's, but i feel they are unneccessary for the things I do. People say the HBAR is better at handling and dissipating heat, but I have never fired fast enough to truly get the barrel super hot. I think this may be a problem with full auto guns more than with civilian rifles. I think the slight weight savings of the M4 are worth it.
So, if I were in your place, this is what i would get: The M4 profile barrel with a flattop upper and the removeable carry handle. I don't know much about the tactical brake that J&T uses. Given the time and money, I would rather get the normal barrel and send it off to Kurt's Kustom (listed in the industry section) and have his thread and permanently attach one of his mock flashhiders on the muzzle. I think it would be worth contacting him and asking for a price quote. I would get the A2 stock or the fixed M4 style stock, as the ergonomics are similar. Some people find that the CAR stock's buttpad is too small and the straight angle is uncomfortable, so the A2 or M4 would be better for most. Either the duckbill or the ambi-ergogrips would be my choice.
As far as handguards, that's a tough choice. I have one with the M4 double heatshields, the others have CAR handguards, and I have an RAS on the way for the M4 upper that I am getting. Some people feel that the M4 handguards are too bulky. I don't feel that much of a difference in the CAR and M4 handguards in all honesty. Some also say that the M4 handguard interfere with red dot/reflex optics when mounted on the flattop. This is a problem easliy solved by mounting accessoris for the optics.
If you are willing to spend the money, get the RAS, a free floating one if possible. The free float RAS will allow you to mount optics on the RAS without risk of losing zero in adverse conditions. The only downside is that free float handguards require tools to remove. Cleaning under the handguards will require you to use a tool to remove the set completely. However, routine cleaning will only require you to blow out the inside with some canned air. I think a flattop and a RAS will cover you for any contingency.
When the ban lifts in September 2004, you can just take that same rifle and install preban components onto it. A collpasible stock can then be used to replace the fixed stock. You could send your barrel to Kurt's Kustom and have a real flash hider installed. Or you can get a new barrel and install that.
I think Dissipator may just be a catchy name. it could also mean that it has less barrel exposed, so less heat is felt and therefore "dissipates" the heat.
There are many horror stories about American Spirit Arms (more so than any other company). There is a story that someone with a faulty rifle tried to return it to the owner of the company for repairs and had it [forcibly] tossed back at him. they just have reports of poor customer service, a rude owner, and more faulty products than anyone els. There is also rumors circulating that they are going under. A handful of people have had good rifles from them. I wouldn't take the risk, especially with bad customer service.
I hope this helps, please feel free to ask any other questions before you buy. I wish I had been able to learn a lot more before I first purchased a rifle.