Are the cards you have maxd out? Do they show late payment history? If the problem is that hte balances are maxed out, do you have the ability to get them at least 50% below the limits? Down to 30% over all? The maxed out cards, if that is the case, is probably whats hurting your score overall. If you could lower balances just before your statement date and have them report the lower balance, you may just see enough improvement to apply for a better card. Maxed out cards hurt you as much as a collection.
Just a word of advice, if you obtain new credit please be careful about your limits. If these cards are hurting you enough where you need to BT with the limits you posted here, you probably have all the credit you need for the time being. Just friendly advie because although we want everyone here to have the best reports possible given the circumstances, we also don't want to open the door to future credit problems.