Yikes, that BML sounds like bad news.
I use CC for online purchases because of my card's credit insurance. If I have a problem with a vendor, I just call up my CC company, and they usually take care of it, and can reverse the charge.
And you don't have to have a lot of credit cards to have good credit. You just have to be financially responsible. When BMW ran my credit at the dealer, the SA came back to me and said "congratulations". I asked "what for?" and he said I had one of the highest credit ratings they had ever seen. It was 830. I didn't even know, and I only have one credit card (not even that high of a limit either).
When I got out of college, I *thought* I was making good money and started using credit cards more because I thought I could always just make the payments. That lasted about 3 years or so, until I finally woke up and saw that I had a balance on 3 credit cards, a student loan, and a car payment. Just making the minimum payments left me with hardly anything left at the end of the month. It sucked.
So I contact a financial service and got on their "get-out-of-debt" plan, and stopped using the cards and worked on paying off all that debt. It took about 5 years, but in 2004, I became 100% debt free. During that time, I paid off my car, student loan, and closed all my credit cards as I paid them off, except one. From that point on, if I used it, I paid the balance off each month. I never let a balance roll into the next month. If I want something, I don't buy it unless I have cash money in the bank. Period. No cash = no buy. I've lived that way ever since and have been able to save up more money that I would have ever thought possible, because I don't have any debt.
So when I went to buy the bmw, I went in ready to pay cash. but since they had 0.9% financing on 36 months, and my savings account gets over 3% in interest, I financed about 9k of the purchase (which I can pay off if I want to). I hate having another car payment, but its only $259/month, and I can pay it off tomorrow if I really want to, so I guess I can live with that.