Youd be a fool to only use the rely as a tv display.
Once you play around with multimonitors theres no turning back, consider running both.
Didnt think widscreen monitors suited PC games as the resolution isnt always supported and then your using a stretched variant but the dell is going to look MASSIVE and much better with games as the rely does look funny even for general surfing from my own personal experience.
Be nice seeing the new 20" on the wall though, and not fussed on their stands, however I dont think tv in one corner and monitor in the other is the best soloution unless you want to end up with a squint. NE/NW eyes, or did you mean putting the rely in the middle of the desk?
Personally Id recommend a self made wall display unit for storage either side and have the two monitors built in the middle wall mounted, perhaps the widscreen on top via a retracting adjustable arm bracket.
Only an idea