Well, a fan will eventually wear out, heat sinks won't. Other than that, there should not be much difference. If you can still hear the fan when music is playing, you need to turn your music up or get a quieter fan.
An old DC300A would be a great choice for your sub amp in my honest opinion. There are 3 of them currently on ebay and it does not appear that any of them will reach $200. This would give all the quality power that you could ever want to your sub and is likely to be 10 times better than the new Crown amp that you are looking at. These amps sold for around $1200 to $1300 in the mid 70's and the only thing that Crown makes today that would compare is over $3500, their Studio Reference. They have always had one or two expensive amps in their lineup and they were always world class amps. The old DC300A was considered by many to be the best amp of it's day and would be better than most amps that are being made today. Naturally, there are better amps but I would hope with the costs rising into many thousands of dollars and up to 100k or so, that they would indeed be alittle better. As I said before, my son is still using my DC300A that I bought new in 1975 and it works just fine. Still a very fine amplifier.
Bill