pioneer sx 780 receiver


I just recently purchased this receiver , curious how it would sound with my Klipsch Heresy 1 speakers.
I have been using Wyred4sound SX1000 with an Audio Research LS7 Preamp.
My question is: Why would this vintage Pioneer sound as good as my system?
Any Opinions ?
Thanks
rocky1313
i picked up a 780 for $10 at a garage sale and was shocked at how good it sounded--it was significantly better than most of the vintage hk, yamaha and marantz i've cycled thru. since it was sitting unused i ended up passing it along to a buddy (a move i've regretted), who uses it for vinyl is similarly rhapsodic. now, you're heresys are easy to drive and i wouldn't be surprised if they paired with with the 780--keep us posted.
Because the Klipsch are not capable of sounding any better , at least not without tubes .