A 5400rpm drive is not a speed demon. There are lots of options that are faster. In rough ascending order of increasing speed:
- a larger 5400rpm drive will usually be (a little bit) faster, because more data is packed into the same space, so it's read and written more quickly.
- a 7200rpm drive will (all other things being equal) be somewhat faster, because the spin latency is lower
- a 10000rpm drive, like a Velociraptor, will be a bit faster still - I would expect a 600GB Velociraptor to cheerfully slaughter your current drive
- a 15000rpm drive will be faster still, but I'm not aware of any SATA 15k drives at the moment - all the 15k drives I've seen have been SAS or another SCSI variant (or something even more exotic). They are usually rather low capacity, and entertainingly expensive - mostly used in enterprise systems.
- a Solid State Drive (SSD) will be MUCH faster again, but... SSDs are rather more expensive than rotating magnetic hard disks, and offer lower capacities. For a reasonable price you can get a 60 or 120 GB SSD that will astound you with its speed. You'd be best advised to use the SSD space selectively, and retain your existing drives for the rest of your data. You could, however, get a 480GB SSD - just be prepared for it to be $2000.
- anything faster than a SATA attached SSD is getting seriously exotic - there are things like PCI SSDs, for example, but they are quite expensive.
I would recommend you consider getting an SSD, if you are willing to spend the money and the time to set it up. Failing that, you could replace one or both of your 500GB 5400rpm drives with 1TB 7200rpm drives; 1TB 7200rpm drives are quite cheap these days, and you can use Ghost, or similar software, to copy your data - that would be the minimal effort solution.