For future reference to others, as of now, SDD run at about 2 bucks per gb. If you don't want to spend that type of money, the next fastest way is to buy a Western Digital Velociraptor harddrive. If I recall correctly, it is pretty much 2 harddrives smashed into one running on "RAID 0". Pretty much, that splits up the data into 2 drives so things downloaded twice as fast (hypothetically).
A 600gb one on newegg.com will run you about 300 bucks. The thing is that I'm not sure if the heatsinks on the Velociraptors will fit in the drive bay of a PS3. I believe there are versions without heatsinks though.
600gb Velociraptor - 300 USD
http://www.newegg.com/Product/Produ...554&cm_re=velociraptor-_-22-136-554-_-Product
600gb Velociraptor without heatsink - 270 USD
http://www.newegg.com/Product/Produ...555&cm_re=velociraptor-_-22-136-555-_-Product
And if that is still higher than you would like to spend, try the Western Digital Caviar Black series harddrives. But make sure you choose the one with 64mb of "Cache". To put it in simpler terms for those who are not big computer geeks, the more cache you have, the faster things are.
To keep with similar sizes,
here is a 640gb Caviar Black 64mb drive for 70 USD
http://www.newegg.com/Product/Produ...544&cm_re=caviar_black-_-22-136-544-_-Product
But to show how much cheaper these drives are, here is a 2tb (2000 gb) 64mb harddrive for just over half the price of a velocraptor
http://www.newegg.com/Product/Produ...456&cm_re=caviar_black-_-22-136-456-_-Product
That is an extreme especially for a PS3, but it just shows the price difference. The speed difference between a velociraptor and a caviar black 64mb is small, so if you cannot decide on which to get of these two, I suggest the caviar series.
Solid state drives are still too expensive at this point and time and you are really wasting your money right now (in my opinion). If you are interested in a SSD, I would wait until Q3 or even Q4 of this year. I predict they may be dropping to about half their price by the end of the year