Should I get Dolby B decoder for my open reel deck

I'm confused! Recently, I purchased an RT707 reel deck and upon enquiring about where to buy pre-recorded reels some one on Audiogon tells me about getting a Dolby B decoder. Problem is, NONE of the pre-recorded reels I own (about 14)were recorded with Dolby, at least the boxes don't say so. I think this is a little odd, considering they are all from major labels. Could it be thagt they WERE recorded with Dolby amd merely not listed?
Dolby B was used as a method to reduce or eliminate tape hiss. There are Dolby B recordings, but the boxes are clearly marked as such. You don't need a Dolby B decoder to play tapes on your deck. Maybe 90% -95% of the reel to reel tapes sold are not Dolby B.
Dolby was most often used to reduce hiss on cassette tapes, due to restrictions imposed by the slow tape speed (1 7/8 ips, I believe). RTR decks, running at speeds 2-8x faster, aren't subject to this problem, and dolby processing is typically not needed.
The very best source of pre-recorded open reels was a small company named Barclay-Crocker, which licensed performances from a number of the majors, and did them in very high quality Dolby B. They had several thousand titles, as I recall. At least on the East Coast, any used tapes for sale will usually be at least 50% Barclay-Crocker, and need a decoder (if you can find one).
The Phase Linear model 1000 Autocorrelator noise reduction system is what I use with my RT 707. It is simply incredible. MOST reels were not recorded with dolby but there is still significient hiss from the tapes. The Model 1000 has user adjustable settings that allow you to fine tune the amount of noise reduction without comprimising high end frequency response. You can get them for cheap too. EBAY!!! Best prices.