I'll let someone else provide info on what Dish will or will not do, but as "webbydude" said, I kind of doubt that they will give anything extra unless it's needed for the equipment they are furnishing.
I believe there may be two current software versions for the 508; P363 and P364.
http://www.dishnetwork.com/content/customerCare/technical/software_versions/index.asp
I'm not sure if the screen would should something different if you had a DPP Twin instead of a DP Twin. Maybe someone else has more knowledge. Otherwise, it sounds like you have a Dish 1000 installed to receive 119, 110 & 129. The Dish 1000 comes with a DPP Twin and a DP Dual.
It is possible the DPP Twin was replaced with a DP Twin when the DP34 switch was installed.
To add another receiver, you are going to need another Switch. You can buy a DPP44 for under $200 and use the DP34 for a spare; or you can buy another DP34 for under $70, and connect it to the current DP34 which will allow you to have upto 8 tuners.
As stated before, you can use 2 diplexers to back-feed one of the 2 other rooms using the ViP 622 TV2 Output.
However, since you prefer not to get another switch, then maybe you get a splitter, and backfeed the 622 RF Output to both of those rooms. Then you could also, turn on TV1 Output, so that both tuners are being backfeed to those two rooms. Then you could buy another UHF PRO remote for the other room to control TV1 when no one is watching it downstairs. Each room could watch a different program, and if they watch recordings, the 622 could record 2 new shows at the same time.
DPP44 - 4 sats, 4 receivers - upto 8 tuners
DP34 - 3 sats, 4 receivers - upto 4 tuners
DPP33 - 3 sats, 3 receivers - upto 6 tuners (not available yet)
TV/Cable Splitters - splits same RF signal to multiple locations; usually can be reversed to combine separate RF signals.
Diplexers - Will combine and then split, 1 sat signal and 1 RF signal; but not 2 of same.
DP Separator - Separates 2 satellite signals, which are combined by a DishPro Plus LNBF or a DishPro Plus Switch. Will only work on a DishPro Plus Receiver (Dual Tuner).
You now know as much as the rest of us.
EDIT: TV/Cable Splitters that work in the higher frequency range will also split a satellite signal; but except for in limited circumstances, it will not work (properly).