Murphy isn't a striker - he's played on the left or behind the Striker.
Also - take Brighton's bid with a pinch of salt. Brighton are well aware that Sheffield United are interested in O'Grady, so it's most likely a clever bid to get Murphy at a reasonable price, to help smooth over the O'Grady dealing.
Although - if what's being quoted is correct, Brighton have bid 1m for him. Personally, I wouldn't pay this sort of money for him - and if he does sign, it's another massive gamble for Brighton, much like Baldock was - and look how that one turned out.