Killer vintage 70's, 80's reel to reel to add to my setup.

The Technics RS1500 and the like, and Otari 5050 would be good choices.  A friend who reconditions machines like both of these for being rugged and maintainable (particularly the Otari).  The only potential issue with something like the Otari is that it was a professional machine, so some of the used machines on the market are very heavily used.  This friend prefers these two over Revox machines from this era because of build quality, but, in good working order the Revox is also a topnotch machine.

Teac/Tascam made some nice semi-pro machines that go for not that much money.  Also, I think some Pioneer machines sounded pretty good, although their compact size did not allow for use of 10.5” NAB reels.

I agree with mijostyn that reel to reel is generally NOT the way to go from a sound perspective.  Yes, there are great sounding tapes out there (I've heard a few), but, the pursuit of a reel to reel system can only be justified sonically in an extremely high end system where all other sources have been refined to a very high level of performance; otherwise tape is a waste of money.  There are very few good pre-recorded tapes available, and so the music selection is VERY limited.  The commercial tapes I heard that I thought might justify a reel machine cost over $500 per tape.  Also, decent machines cost around $20k.  Expensive machines to play a few good tapes may be justifiable, but only in the context of a system that already has top notch digital and vinyl setups.

Perhaps, the other justification is to preserve very good records by recording them to tape so that the records don't have to be subjected to repeated play.  I heard tapes made for that purpose and they sounded quite good.  But, so did digitized transcriptions of records and that is MUCH cheaper to do and digital is recording is more durable than tape and is SO MUCH MORE convenient.

Something to play around with, that would be the proper role of a R2R machine if you did not already have a substantial collection of tapes.  A bit more of a hassle than a cassette machine, nut certainly nicer to look at in operation.

You can find a lot of these recommended machines, including Studer A807, 810 and 80 machines on the Reverb site.  They do not sell things for cheap prices, but, they are generally fair.  It is worth window shopping there.

I don't know if I would say that a system is not complete without a good R2R deck.  If one is satisfied playing a relatively small selection of music, and insist on really topnotch performance when playing those few selections, then maybe, a high end machine is justified.  How high?  Why not insist that only an ATR 100 series machine will do?  

Any model Studer that has been properly reconditioned will probably cost more than your budget.  But, the same company made Revox machines that were intended to be non-studio machines that are nice and much cheaper.  Look for an A 700 or A77 or B77 machine.

THE “new” machines that I like come from United Home Audio.  The top machine utilizes a reconditioned Tascam transport and electronics that are designed and built by them to be the very best; it better be good because it costs in excess of $90k.  You can hear their stuff at audio shows and at their DC-area showroom (very nice and friendly people).  

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.