Dual or Quad Core for my uses? (more details inside)

Hello all! I registered in hopes of getting a response from people on this forum since I cannot seem to find a direct/conclusive answer elsewhere.

I am currently looking to buy a newer laptop. I have considered desktop but due to how I move around often and lack room I am buying a laptop.

I currently have a laptop with a 2.0ghz CPU (T7200 Core 2 Duo), 2gb RAM, Vista Premium 32bit and a Nvidia Go7400.

I play Final Fantasy XI and have been told by many it is a CPU intensive game, . I sometimes run 2 instances of the game at the same time (as in, have "2 of the same game" running but with a different character). My T7200 2.0ghz with 2gb RAM, the CPU shoots to 95%~ (with Firefox running on top, normally watching something from Youtube or something else, watching videos). And on top of that I have a few tabs open for web browsing, and run Winamp or Windows Media Player (watch DVD) on top of my 2 instances of the game.

Needless to say, I'm not too bothered about how the game looks, but running 1 instance + all the apps mentioned above my notebook does fine. Running 2 instances and all the apps above is where I start having performance issues, despite my FFXI instances being throttled down beforehand to a smaller resolution/low graphics, etc. This is of course natural and understandable. i.e. DVDs stutter a bit when I try to skip, both FFXI instances lag/stutter moderately but not to the point where it's unplayable, doing other things on the laptop takes a big longer. This is all expected however.

I am comfortable/satisfied with the way a T7200 2.0ghz CPU runs 2 instances of the game, but with other things on top then it becomes difficult.

I have my eyes on a laptop someone is selling me with 4gb of RAM and a Quad Core (Q9000 2.0ghz) CPU and a very nice graphics card (Ati 4850). I got my eyes on this because I planned to play some newer games on top of what I currently play/do so I think this is an ideal choice, for the price too. (For those interested, it is the Advent 6555, but it is no longer available. This "someone" is has a spare but of course I will take all precautions/checks before handing over the money. For the branded equivalent, look up MSI GT725-210UK)

However, based on my situation, due to my desire to do more multiple things on top of running 2 instances of FFXI, would a quad core significantly improve my "quality of life", so to speak. If 2 instances of FFXI alone can bring a T7200 to 85-95% CPU usage, 3 will be more or less impossible. But with a Q9000 would this let me run 2 instances without maxing out CPU usage?

To sum up, here are some stats to help people answer my question:

1 FFXI instance + apps mentioned = 20-30% CPU usage, peaking at I'd say 60-70 -depending- if I'm in a busy area of the game, but even so it is comfortable to do so.

2 FFXI instances + apps mentioned = 85-95/100% CPU usage, both instances stutter moderately but still playable/tolerable (to my standards), can still watch movies/some stuff takes a bit of time to process

I hope I am clear about my situation/what I am trying to say, and if someone can tell me what they think it'll be greatly appreciated.

Additional notes: I'm not an overclocking fan, I'm not looking to max out graphics/games/performance, I am satisfied with the way everything is, I just want to be able to do more and am wondering if quad core will alleviate my problems above so I can either run 3 instances of FFXI or 2 instances and comfortably do other activities with no or little to none bottlenecks.

So in other words, a Q9000 clocked at 2.0ghz (what I started with but only 2 cores) with 4 cores, or a slightly better clocked dual core in the region of 2.5ghz to 2.8ghz? (Which would mean an alternative laptop, but there's plenty of those around)

Also, I have attempted to set the affinity for both FFXI instances but have noticed no improvement or difference.