Nautilus 801's- Cheaper Amplification

Hello all. Would appreciate your help with the following situation. Recently purchased b&w nautilus 801's at a great price but still cleared out much of my budget. Wondering if anyone has any ideas regarding more affordable amplification for these brutes (like 3-5k for 2 used amps with at least 100 watts power ss)
from everything i have read they really do sing better with bi-ampliciation and so i am attempting to go that route.
the speakers are serving a dual role 50% ht and 50 % 2 channel
i have a sf line 1 with upgraded nos tubes
acurus act 3 with abm
rega planet cd player
thanks for your help in advance