The price for a SATA HDD has been steady around $80 for many years now, I don't think they will get any cheaper and if they do it will only be by $5-$10. Take the cost of the adapter away from that $80 and you will have only paid the difference and gained a TON of extra storage and a 5 year warranty(Westrn Digital).
If I am not mistaken you should be able to reuse your old case.
I would buy Corsair for your RAM.
Last edited by jakewash; 01/21/12 06:17 PM. Reason: warranty clarification