My current boat is an 2002 TR20 that was repowered in 2007 with a 225 proxs. I bought the boat 2 years ago from the widow of the original owner. It had 18 hours on the new motor and has warrantee until this summer (July 2012). I was happy to find it because the price was in line with all the other 02-03 boats I had looked at, but I was shocked when I got it home and found the invoice for the new motor. I paid the same amount for the boat motor and trailer as he had paid for the new motor alone 2 1/2 years earlier.
The warning here is this: If you will truely hang onto your boat after repowering, go for it. But if you even think for a minute that you will be wanting to upgrade, then don't spend the $ on the new motor. It doesn't increase the overall value of the boat much at all. In fact, after a couple years it will only sell slightly higher than any other 99 tr19 in similar condition.