Regarding your choice of machines, you must first decide what you need. If you are going to collect high end audiophile tapes, you will need 15 ips speed, 10.5" reel size capability, and 2-track playback. If you have, or will be collecting 4-track tapes, you need 4-track playback capability. If you are going to record your own tapes, you need to decide whether you want 4 track recording capability or just 2 track capability. If you are going for 4 track playback, you should decide if the ease of reverse playing is something desirable.
I like the Technics line of machines. The 1500 is a 2 track machine that also has a 4-track playback only head; just flip a switch and it will play back 4-track tapes. It operates at three speeds, including 15 ips. The 1506 is a 4-track machine (meaning it can do 2 track record and playback and 4-track record and playback). The 1700 is an auto-reverse 4 track machine. These can be had well within your budget, although mint and never used machines cost considerably more. At your new budget, you should be able to get a fully reconditioned machine that has been lightly used. Plenty of machines were made, and there are plenty of parts available.
The Revox PR99 mentioned above is also a nice machine that has a lot of parts availability.