Need information on tape drives.

Having a lot of TV series I was wanting to backup I decided that instead of buying a lot of DVD discs it would be easier to store everything on tape. I don't have to worry about scratches appearing, or accidentally dropping the thing as easily, plus since some DAT tapes have 400GB of storage, this would seem to be the perfect solution. Only one problem...I know absolutely nothing about tape drives, or what kind of tapes I should get.

I have looked at newegg, and have noticed that recent models are around $350 and up, and have noticed that they are different types of tape. Also, when looking at ebay, I noticed that they are some outdated tape drives that go for $100. Why is this? Is it that only certain kinds of tape can be used on them (in other words the older drives won't accept newer tapes that have well over 200+ GB of storage)?

Anyway, sorry If I sound painfully ignorant on what I'm talking about, but as stated earlier, I know nothing what-so-ever about this, so any help would be appreciated.

Here is the tape I found that had 800gb of data on it.

http://www.newegg.com/Product/Product.aspx?Item=N82E16840124001

I assume of course that means 800GB when compressed, because otherwise, it would just be 400GB. Twice the storage capacity, but twice the chances of data corruption I guess (assuming of course that compressions when applied to hard drives also apply here). Also few quick questions; would this drive be compatible with the above tape?

http://www.newegg.com/Product/Product.aspx?Item=N82E16840161016

Also would this tape be compatible with this drive as far as writing purposes?

http://www.newegg.com/Product/Product.aspx?Item=N82E16817113405

Final question can these tapes be written to multiple times? In other words, delete the old data, and replace it with new data (kind of like a floppy disc)? Also what is the total transfer speed of a USB device? I imagine it's going to be less than 80MB/sec, so I imagine at least 20-40MB/sec.