v1c:
The main difference between 71/72 and 81/82 is an extra 10w output power per channel for the 81/82 and THX Ultra 2 instead of THX Select 2.
The difference between the THX Ultra 2 and THX Select 2 as quoted from THX is
" THX Ultra2 Certified products bring the cinematic experience to larger
home theaters, 3,000 cubic feet in size, with a viewing distance of 12 feet or greater from the screen."
and
"THX Select2 Certified products are for medium sized rooms, up to 2,000
cubic feet in size, with a 10-12 foot viewing distance from the screen."
Therefore the 81/82 would only have greater benefits if the room and viewing distance is greater.
I went for a 71 based on the room size rather than the difference in performance. There is a lot of subjective opinion as to how significant the difference between 71/72 and 81/82 is , some say there is a big difference some say there isn't , to some it's worth it to some it's not. The 81/82 is the better amp on spec but the 71/72 is still a pioneer and has still been air studios tuned so unless you have a big room a 71/72 should be more than sufficient. I have asked a dealer about the difference between 71/81 and 72/82 and basically was informed performance wise hardly noticeable. However the newer 73/83 range is being reported as having a significant difference to the 72/82 range therefore unless you are getting a 73/83 you may as well get a cut price 72. The 53 is not an SCLX it's a VSX it's hasn't got the Susano lineage so i wouldn't consider it a viable option against a cut price 72.
V1C thanks for explaining the differences. I have a reasonably small room, 4 x 4.5 m2 so would probably then look at the 72. Can't really demo the 72 or other models so can't do a like for like comparison. I'm upgrading from an Onkyo TS-XR806 receiver and I'm assuming the Pioneer models are a significant ugrade?