Prepaying is a good way to go as you almost certainly will not accrue any finance charges. Certainly ask for an increase in credit line . Credit line is usually tied to % of income and credit rating. If your rating is A1 then it will rest soley on your income. Assets are generally not all that important as it is unsecured debt.
It was said that they can not check your limits on other cards, this is actually wrong. When the credit analyst pulls up your report they can see what all your limits are and what all your balances are.
If you are not already doing so make sure that you include all the gross income generated by everybody in the household in the application/request for increased credit (Give the reason for requesting credit line increase as: income has changed). Incidentally unless your credit rating is is iffy (either because of bad history or very little history, or little history of other cards with substatial credit limit) they generally DON'T check up on income.
[This message has been edited by Mvic (edited 07-31-2000).]