As a PC Gamer you are going to be looking at more and more MMORPG and downloadable content. Steam is probably your best bet if you want to focus exclusively on the PC gaming side of things, there is a wide variety of games for a multitude of tastes in their marketplace.
I would start there Before I dropped a whack of money on a new console (which requires a whack of extra money to get it up to snuff, when I bought an Xbox 360 I ended up dropping close to CAN$1000). Also realize that a lot of the major titles coming out for consoles are often times easily and eventually ported to the PC (These titles start their lives on PCs and PC is not considered a competitor platform to developers)
As a PC exclusive gamer, if you did buy a console you would gain access to more game titles, and don't listen to those guys who say otherwise, that's PC gamer fanboyism, we all know it. Consoles are intrinsically going to have a constant flow of games tailor made for the platform because that is all they are about. No time wasted on developing word processors, web browsers, and the next Adobe Creative Suite.
Also as a PC gamer, the Xbox 360 would likely be tho most comfortable transition as far as hardware, software, and overall theme is concerned. Next would be Sony's system, but it is this generations Game Cube except for the fact that the Cube was inexpensive.
The Wii may be cheap, and it may have mouse like motion control, but it is definitely the furthest from what you are used to.
Summing up: Start looking for downloadable content centres i.e. Steam. if that doesn't get you enough of that good gaming stuff, check out consoles, my immediate recommendation for a dosh concerned PC gamer would be an Xbox.