i'd take cahill no doubt about it. i think he's a class player even though bolton haven't played too well of late. if you look at englands ageing centre halves in terry & rio you can't help but think cahill will be a regular part of that side if he signs for a top 6 club.
i'd only make another signing if the right player became available e.g. hazard and the likes. wether we can attract that sort of player is debatable. but if we have the cash then why not make an attempt?
as for a striker i don't think there should be any sort of 'quick fix'. we need to go about it in the right way and sign a top quality player not fork out for someone we may struggle to sell in 6 months time. we lacked funds under rafa and hodgson and those 'quick fix' signings never really turned out well for us. think joe cole, poulsen, konchesky, morientes etc.
we have good finaces so we shouldn't lack any ambition in the transfer market imo. but we should only make a move if the right players become available.