i was never a fan of the 810e when i had it. i was running an SVT4-pro through it and it always seemed weak to me. especially if i was using a 5 string. i always felt like i had to choose between having a big bottom and having good definition in the mids and highs. i was always jealous of my friend who decided to go with the 610, because it sounded alot more balanced to me (and it was smaller)
i happened to run across an 810HPC used for $500 so i decided to give it a shot. all i can say is WOW. it is everything that i expected an 810 cab to be and more. it has that same tight focused bass that the 810e has, but does not sacrifice the low end at all. plug a p-bass into this thing a slap around for a few minutes and it will feel like bullets are flying out of the speakers at you. i just turn the horns all the way down and it keeps the clatter and hiss out of there.
the only down side is that it comes in at about 210 pounds, so it is significantly heavier than the 810e.