My personal recommendation is to stay away from Dell, focus on parts instead of name brand, and the respective warranty programs each manufacturer provides.
I'm assuming you're looking for pre-built machines instead of build-it-yourself enthusiast types.
Based on this, I'm going to look at what Future Shop has listed online.
You will want to stick with the Core 2 Duo/Quad or Phenom processors for the best price/performance ratio. If you want games, you will need a graphics subsystem or future upgradability. Definately get a system with an ATI Radeon or NVIDIA GeForce graphics system, and avoid integrated solutions like Intel Graphics.
If you want a solid system that has a fast Phenom processor and a good starter graphics card in the Radeon HD2400, try this system:
http://www.futureshop.ca/catalog/proddetail.asp?logon=&langid=EN&sku_id=0665000FS10100118&catid=
That system has 3 gigs of memory and a Radeon based graphics system so its more than sufficient. Combined with a Phenom processor it should be sufficient, although the HD2400 is not top of the line graphics and the 667MHz memory also isn't the fastest on the market, but if you aren't into games it doesn't matter. The 500 gig hard drive is sufficient storage space.
If you need more graphics power and/or intend on doing high end gaming, I'd recommend this.
http://www.futureshop.ca/catalog/proddetail.asp?logon=&langid=EN&sku_id=0665000FS10100503&catid=
This is obviously a higher priced, faster machine. The Core 2 Quad processor at 2.66GHz is significantly faster than the Tri-Core Phenom at 2.1 Ghz, it has a slightly better graphics solution in the GeForce 8600GT, and it has much faster memory at a full 1066 MHz bus with 4 gigs, and that means its packed with 64 bit Windows Vista instead of 32 bit preinstalled.
Obviously better costs more, so if you want something that has power for games and more, I'd go with this system.
Really it depends on what your budget allows. If you don't run games, get the Phenom system above, if you want better performance and higher 3D rendering capability, get the HP system.
If you need further help, just go to a local computer store and ask around.
Don't get a new system with less than 3 gigs of memory or a 2 GHz dual core system. In my opinion there's no reason to stop at dual core, get a tri-core or quad core system with a non-intel integrated graphics solution.
You'll thank me later for repeating not to get an intel integrated graphics solution, its possibly the most important selection in your computer. If in the future you find out that your banging new system is great, but was stuck with an intel integrated solution without any upgrade slot, you've just wasted hundreds of dollars on a system that screwed up possibly the entire reason you wanted a new system.
