You can absolutely use an old power amp with a new pre-amp. However, the good news is you don't have to look for something "from the '80s". At Audiogon you can find "old" power amps less than five years old at your price point.
Don't get too hung up on watts. There's a lot to amp choice other than published watt specs. There are many excellent amps in the 50 watt range.
There is no reason why an integrated cannot be as good as seaprates. It depends on how it's designed and built. For $500, I think you should be looking at a good integrated rather than try to stretch the dollars out over separates (and an interconnect). I very much doubt that you can find separates totalling $500 that would best a good integrated at that price.
Rotel, NAD, Cambridge Audio are all very good value for the money. I would prefer the Rotel from those three but it's your preference that matters. You could also look at Arcam. However, my personal favourite for small integrated amps is Creek. You can find them at your price point but they sell fast.
Don't get too hung up on watts. There's a lot to amp choice other than published watt specs. There are many excellent amps in the 50 watt range.
There is no reason why an integrated cannot be as good as seaprates. It depends on how it's designed and built. For $500, I think you should be looking at a good integrated rather than try to stretch the dollars out over separates (and an interconnect). I very much doubt that you can find separates totalling $500 that would best a good integrated at that price.
Rotel, NAD, Cambridge Audio are all very good value for the money. I would prefer the Rotel from those three but it's your preference that matters. You could also look at Arcam. However, my personal favourite for small integrated amps is Creek. You can find them at your price point but they sell fast.