I'm looking for opinions here, or facts :)

I have a pair of NHT ST-2's with which I've amped nicely for 15 years with one Adcom GFA-555.

I have the inclination to get another GFA-555 and run vertical bi-amp. This is likely to cost me <>$400 for the second GFA-555.

So that's roughly $800.

Or I could sell my GFA-555 and get an $800 amp.

Any opinions as to which is the best move? Recommended amps that would do better than two GFA-555's?

Thanks