should I upgrade my amp

What ICs, power cords and speaker wire are you using? These may make a bigger change in your system than the amp or preamp depending on what you are usig now. I compared 12 amps over the past four months and there wasn't that big of an improvement over better cables.

I agree and second bob bundus's comment concerning the pre-amp it is the most important component in your system.

Chuck

I don't know for sure whether I would go preamp or amp. If I were to change the amp I would consider going with a Forte 4a and maybe even two of them.

I use a Jolida 1000a integrated tube amp with Spica TC 50’s. Give tubes some thought, I find tubes takes some of the glare out of the Spicas.

The Musical fidelity amp is killer for the used price. If you like the 545 sound you'll love the MF amp and preamp. I agree that the preamp is as important as the amp, when funding allows I would upgrade both to MF gear. If you don't need the extra power I would avoid the Adcom 555 like the plague, the 545 sounds so much better from top to bottom, but on power hungry speakers it does clip easily....