Historic's are Gibson USA Custom Shop recreations of original (closer than production models but not 100% spot on as the originals) R8 is plain top 1958 standard model, R9 a flametop 1959, R7 a 57 Custom etc etc.
I wouldnt concern myself too much with chambering if the guitar has sweet tone. I prefer heavier guitars but I like mahogany/maple top bodies. A lot of the historics are chambered (bigtime) and come in around 8-9 lbs. Some of the modern weight relieved 2012 standards weigh ovev 9 lbs. My traditional with the old school swiss cheese weight relief weighs 9.6. The new 2012 trads have no weight relief and are weighing in the same 9-10lb range. Its the density of the wood
I also say buy used to save some money. I couldnt find a used R8 for 2k when I bought one but they do pop up from time to time. I bought my trad + used when they were $2200+ out the door in stores, I got it for it $1875 shipped. I took a gamble buying with out playing but felt at the time I got a good enough deal I could easily get my money back if I didn't like it so the risk was minimal but the reward was great

I kept it. If you buy online (you have more options) find a retailer who has a return policy.