I can understand your apprehension, but since I intend to use the F3 as a boot drive for my LAN rig, I can't justify paying for a lower performing drive, even at 2TB. In your situation, it would make sense to go in for a 2 TB. I've definitely seen 1.5TB WD Green drives for like, $100 or $110...but I can't stand the 5400 RPM drives, even if they're only storage.
Don't get me wrong, I'd still pull the trigger on one if I had the cash. But I definitely understand the alternate view. Personally I don't mind the 5400RPM's for storage. My main rig has a 640 Black for the OS and 3 Samsung EcoGreen 1TB's for storage. I've found that the only area where the 5400RPM's show signs of being slower is during extremely large file transfers/copies. Although I'm beginning to think that has more to do with Win7 than the drive itself.
If I keep the transfers to around 3-4GB at a time, the 5400RPM's stay at high transfer rates, similar to the 7200RPM Seagates and almost identical to the 7200RPM Samsungs I have.
It's all a matter of preference I suppose. Personally I'd take a $99 5400RPM over a $70 1TB 7200RPM because I'm space confined. I've had a bad year with hard drives though, so if it's not a proven reliable drive I'll steer clear for now. Unfortunately I've seen way too many drives 1.5 and 2TB in size fail, across all the manufacturers, both current and early production