Ok, I'm a little confused here. The 510 is stereo, the 30-A is mono. Do you have a pair of 30-A amps? Both pieces are nice vintage gear and have a solid following with good potential. A single 30-A won't fetch you nearly the price of a pair. Condition makes a huge difference too. Ebay might get you anywhere from 50-99 for the pre and 100-200 for the amp. A fully restored pair of 30-A amps can go for big bucks. Check out radiomuseum.org for more info. The preamp is kind of an ugly console mounted unit. If the chassis and faceplate are all one big unit it is worth much more than what you will see on radiomuseum.
The speakers might get a couple of bucks on ebay?
The speakers might get a couple of bucks on ebay?