Crossbow7- Yes the particular reason being that the computer is a biggy, with a great deal of umph. Before the disaster it had 2x512 ATI 4870 with crossfire for ultimate gaming. These cards are no longer obtainable, (apparently)hence the query. Thanks for your interest.
OTT_B- Please see my reply to Mr. Crossbow7 above. I shall be looking for two very good cards, not just the one. Thank you.