I like Bushy bbls alot. They shoot very well. I have several, including a 16" HBAR. I really like the carbine, and it's a real tackdriver, but it's a lot heavier than my other carbines. As a result, it doesn't go out as often as its buddies that are lighter. I've thought about scoping it and putting a bipod on it, sort of making a po' man's DMR out of it, coz it's soooo gosh darn accurate. Like you, I am not made of money, and if you are going to have only one AR for a while, I would recommend that you reconsider the decision to go with the HBAR. There are other configurations that maybe more versitile for your needs, but you didn't state your needs/expectations for this carbine.
Just my .02!
ETA: Good call on the M4 ramps! You don't need them to have a reliable weapon, and Bushmaster doesn't offer them anyway. Yes, I do have an M4gery that has the ramps, but I have not noticed that it feeds any better than the Bushy bbls without...