I think you're looking too much into it. I don't have any interference with BT and 802.11B/G wi MS Bluetooth mouse. You might want to look into interference with cordless phones in the house. I do get interference with my cordless...
Here are the system requirements :
MINIMUM SYSTEM REQUIREMENTS
Intel® Pentium® III, Mobile Pentium® III, Pentium M, Celeron - 1.2 GHz, or equivalent AMD® processor, or faster
Intel, AMD or 100% compatible motherboard chipset...
I personally use it on my 600m. Its the same as if you were to go the power schemes, but faster because it sits in the system tray. Give it a try it doesn't do any harm. If you don't like it, it easily uninstalls.
Do a search for...
Changing to the Dothan will not give you noticeable increases. If you upgrade to a 7200rpm hard drive and have a least 1GB of ram you would probably have a computer that runs just a good as a 2GHZ Dothan in terms of performance IMHO. ...
At work I have a IBM T40 and use a NEC 19" LCD1960NXi monitor as my extension. I'm not a developer/designer, but it works for with muptiple MS Excel spreadsheets.
I originally didn't get the extended warranty. When the year was almost over Dell sent me a letter if I wanted to extend to a 2,3, or 4 year warranty.
I recommend that you get the warranty ASAP if you are considering it. Otherwise...