I auditioned both the rf-63's and 83's in my house and liked the 83's better. I agree with Fotog about the klf-20 vs the 30's as I owned both and liked the 20's better. The rf-83 just filled up my room better and had a more distinct low frequency response. Now, both speakers sound incredible and my listening environment is different from yours so take that into consideration. Plus, as another poster stated, it will cost you more to buy the 63's now and then upgrade to the 83's later if you get the bug. I dont think you will be unhappy with either speaker.
On another note, have you shopped around for prices on the RF-83's? There are authorized dealers out there where you could get the speakers significantly cheaper than what you said you can get them for. I just purchased the RF-83's and RC-64 recently from an authorized dealer so you can contact me for the information. Hope this helps.