w6v2 is a very nice SQ driver.There's not many here that I've seen directly recommending SQ oriented speakers - the main recommendation in your budget range is the Rainbow Germaniums.
Link to them here -
http://www.woofersetc.com/index.cfm?fuseaction=product.display&Product_ID=7041
There's a dealer on here for them - I'm not sure of his name, but I can bet someone else can tell you here that can give you more information on them. These speakers would also fit fine, too.
If you wanted to go higher - http://www.woofersetc.com/index.cfm?fuseaction=product.display&Product_ID=4749 - the Morel Supreme's would be one way to go. These would have a better frequency extension, but I'm not sure on the difference between sound quality. I haven't heard any direct reviews of these, but the reputation of the company can speak for itself - and these are their top of the line models. They also fit, I checked that - most of the focal models I looked at were either fairly cheap, lower line, or they were 77mm and up. If you can fit that - then you should take a look - otherwise, yeah.
As for subwoofers.. For pure SQ - I'd say something like the Si Mag 4. A pure SQ oriented sub. Other ones to look at are the IDQv3, and the JL w7 model.
You probably won't see a whole lot of difference between them - but I put them in the order of SQ onwards, based on reviews I've seen. But honestly, you won't see a whole lot of difference between them - imo, at least.
As far as amplifiers go - you can't go nearly wrong with the JL Audio amplifiers. They're smaller than others, compact, and they are extremely well made. Like it's been said, they're moderately expensive, but I'll say for their amplifiers, the price is worth it at least. But, other extremely good options to look at are the ARC amps, as those are extremely good. Run a bit higher than the JL, most likely, at least for the top of the line models, and the lower will run about the same, but that's going to be as far as my knowledge goes for what would be noticeably better. And I can't say for certain it would be a noticeable difference to the ears. Again, I'm still going by reviews - I'm slightly lacking in actual experience listening to all these, especially side by side as would be needed.
You'll most likely need to pick the pair of components you would want first, and the subwoofer(s), and decide on the amplifier from there - based on the amount of power the speakers can use. I'd also make the recommendation of running the front setup active, with a 4-way amplifier (i.e., running the tweeters and woofers off a channel each, rather than running an amplifier to the passive crossover), which would allow you more flexibility over how you want to run the speakers. But, if you want to avoid the complexity of that, you'll want to go by the bridged power - you'll bridge the channels on the 4-way down to two, and power each set off that. So for the rainbow germanium's, you would want something approximating a 150 watts RMS to each side bridged @ 4 ohms.
Now, I'll let you sift through my post here and find the useful information.
Also, as a side note - this does feel sort of odd. I'm giving recommendations to someone with a GT-R, while I'm driving an old '96 Infiniti G20 for myself.
I think we should just put in sony xplodes, and you can send me the remainder of the budget -.-
Anyways, now that I took it slightly off topic - nice car. And DIYMA might be a bit better. They are more SQ oriented there than most here.
IMO sounds much better then the W7 model.
I do like the 8W7 though.
