Hard Disk Drive running low on space available. Any suggestions?

[thiago]

Just a question to you all:
I'm running low on space on my 500GB external HDD.

Here's the situation that I need help to think through:
1-I would want also to boost the performance of my desktop which has now a 250GB HDD (making a RAID 0).
2-I want to have only ONE extrenal HDD (1TB).
3-Solution must lean towards more space available for external and internal drive plus improvement of the desktop's performance while keeping a low bottom line price.

Now bear with me on this one, if I get a 1TB drive, should I move all of the stuff that in the 500GB drive to the 1TB, formatting the 500GB and then buying another one (same model of 500GB) to do a RAID 0 (improving performance but losing 500GB)? BUT then I would have - already only 500GB available on that new (1TB) drive..
or
Like I said, my desktop currently has a 250GB HDD, so do you think it would be better to buy another one of the same (250GB drive) to do the RAID 0, put the 500GB as another internal drive and leave alone all of the stuff I have in it there; and just start fresh with a full 1TB external drive?
or
you step in with a better idea (thank you)

Help me please!

Components in question and price:
250GB HDD (In use on Desktop) $60
500GB HDD (normal 3.5" drive in external eSata enclosure [almost full]) $90
1TB HDD (will buy it no matter what) $185