HOWITIS, what hell are you talking about?
Having a credit card can be an amazing thing. Take me for example. I have a Chase Visa card with 10k (thats how i bought my current car) on it right on at 0% APR. Now that sounds terrible but i also have an ING account with 11k in it at 4.5% APR. The intro rate runs out on Feb. 2008; when i clearly have enough money to pay it off. I will without thinking or worrying pay it off without incurring any penalty. And the end of it i will have almost $500 ($300 interest from ING, and $200 in cash rewards) in my pocket. If i had just bought the car on my debit card like you are suggesting, I wouldn't have that. $500 isn't that much, but its greater than $0, which your method would have produce.
Credit Cards, and debt in general, if properly managed will make money for you! Having a debit card is a great teaching tool for students and other irresponsible people. Frankly, by you saying that you only use debit cards you are basically telling me at least that you don't trust yourself to be responsible.
But thats just my opinion, I've made enough (i.e. profit) from properly balancing my cards and debt that my credit rating is 775+. Oh, and i have no car loan, or any other debt besides what i said above (which in my eyes doesn't count since i have the cash to pay it off right now if i wanted).
OP, i would keep both. The smaller limit card can be used for online purchases and such. And just use a no-fee (very important!!) convenience check to transfer the balance over to your new card.