Birmingham have had a second bid of around £3million rejected for Everton striker James McFadden.
And Hibernian have also turned down an improved offer for defender David Murphy after snubbing City's initial £1.5million offer.
Blues boss Alex McLeish is also hoping to sign Aston Villa central defender Gary Cahill on loan for the remainder of the season.
But Villa would prefer a straight cash deal for Cahill who has just returned from a loan spell with Sheffield United.
McLeish will have to splash out around £5million to secure McFadden's services but City striker Garry O'Connor believes he would be worth the outlay.
O'Connor knows all about McFadden's abilities from their time together in the Scotland squad.
He said: 'James McFadden is an unbelievable talent. If we could manage to lure him to Birmingham then he would be a fantastic signing.
'He has worked for the gaffer before and to get him here would be great because he's top class.
'If he came here he would score goals, as he has already done in the Premier League, and at national level, and he would be a great success and help the team.'
O'Connor added: 'I think it might appeal to him. There's a lot of people after his signature but I think if we stump £5million up we would get him.
'That would be the price. Whether the funds are there I don't know, but hopefully the chairman and the board can give the gaffer some money.
'Hopefully the gaffer will make a few more signings. If we bring players in and keep playing like we did at Arsenal, then I think we will be fine.'
O'Connor is delighted to be part of McLeish's starting line-up after having little chance to impress following his £2.65million summer move from Lokomotiv Moscow.
He said: 'It was really frustrating earlier in the season and I think I was a little bit hard done by. But I did well when I came on as a substitute and stayed positive.
'It's great to be playing now and I always felt I could cope with the Premier League and score goals if I was given the chance and got Premier League standard of fitness from having a run in the side.'