Sam, to add onto Steve's comments. Right now, I only know of one dealer who regularly lists large quantities of vintage prerecorded tapes. This is Irvington Music. They are near Portland, OR and have a website
www.irvmusic.com. I have been a long time customer and have had no difficulties returning a defective or substandard product. Their vinyl prices are a bit higher than some other dealers. Since no one else seems to have the inventory of R2R that they have, including a few "masterdubs" that appear in about every list they do, I can't comment much about their pricing. THe vast majority of the list are 4tr/7.5ips, which your A810 probably doesn't play. However they usually have at least a few (this month more than usual) 2 tr/7.5ips. The masterdubs are almost always 15ips/2tr, like the Tape Project. The cost about the same (actually 1/2, but for half a record's worth). The EQ is NAB, not IEC, but your machine can switch between the two. The souind quality doesn't match the Tape Project, but many of them are quite fine. Since some of the masterdubs they get were recorded on Ampex456 or other sticky shed tapes, they will indicate if the tape needs baking. I haven't bought any of those tapes, though I did get one that needed baking, that was not indicated. Occasionally the masterdubs are dolby A encoded, so you need a special decoder for those. Also if you do add a 4 tr playback head to your Studer, you will see that a fair number of the 4 tr/7.5ips tapes are dolby B encoded. Some people can listen to them with a tone control taming the treble. I can't and bought an outboard dolby B decoder.
Larry