I'm a software developer so don't know a great deal about hardware but may as well throw in my opinion! I've had a few MESH PC's...
www.meshcomputers.co.uk They let you "build your own" so you can spend more on whats important and less on what you don't need. They also have a customisation option on each standard model so you can add bits.
I've always bought towards the top end of price range as I need a lot of power for the type of work I do. However, I'd say a budget to middle machine will very easily do what you need it to do. All the cheaper models will easily handle office, DVDs and TV out (as long as you get a TV out connection!). With regard to gaming, this is where the faster processors and higher quality graphics cards come in. With a cheaper machine, the gaming performance will not be fantastic, but it will be ok.
Hope that's of some help
