cassette and chain question

Hi,

With a recent tune up, my LBS recommended a new chain.  I know it was older and stretched, so I agreed.  First ride out I was getting chain slippage in 2nd and 3rd gears.  Looking at the cassette, it is hard for me to determine whether it is worn, but I assume it must be.

The cassette is an 11-23 Ultegra, paired with compact chainrings.  I have a second 11-23 DA ring for the race wheels, which I purchased when I though it would be important.

I would ideally like to get a cassette to be used on hillier terrain, as I live in hillier terrain.  I note that the new 6700 Ultegra has an 11-28.  Now the question (finally).  Can I use the same chain, or will I need to swap chains with cassettes each time?  Not a huge problem with a quick release link, but just wondering.  Is this a bit overkill with compacts, and should I just be looking at a more traditional 11-25?  I will still have the 11-23 DA, so I am looking for versatility here, as well as help on the hills in a race.

Thanks.

Gordon

Edited by kesslergk 2009-06-29 3:34 PM