hmm...How many do you suggest? 1 more 2 more 3 more 4 more or how about I just buy 10 more HD Primes at 150 a pop. $1500 more and problem is solved. Why didn't I think of that?
I've got a quatro and 2 extends, so a total of 8 tuners. I have split it up so there are 4 tuners per broadcast market. This gives me all the Baltimore channels and all the DC channels... and I have never had a "tuner not available" message.
EDIT: I have been doing this for awhile now and have existing equipment, but if I were just setting it up for the first time today, I would just use 2 quatros, 1 for each market.
You could also add one or more TVE devices as a backup for some of your HDHD Prime channels.
That way if all of your HDHR Prime tuners are busy it will try to record from the TVE devices.