I'd go with the Hard Drive. There is no denying the GF3 is a far faster card, but if your V5 is already running every game you have fast enough the what's the point of going even faster except bragging rights?
If your games arent running fast enough and it's beginning to get choppy, then by all means the GF3 is an excellent purchase. If your games are already fast enough for you however your gaining little besides a few DX8 features that arent even being much taken advantage of in current software.
As for the V5's FSAA being blurry, I agree it is a little blurry... but it's still the best FSAA implementation yet made. Certainly far better then that of the GF3.
The HDD on the other hand, it will most definitely yield you a very noticeable performance boost in basically all your uses. Sure, it on't boost your frame rates worth a damn. but loading times and all around Windows usage will be very noticeably faster.