I have a 6 wt and a 9 wt Xi3, and they are powerful sticks. I just got back from the Gulf Coast of Florida, and I used a Rio Outbound Short tropical line on my 9 wt. I was very pleased with the way that line matched to the rod.
It's amazing when you find a line that matches so well with the action of a particular rod. Since the 8 and 9 weights are not too much different, I thought I would opine.
When you get your 8 wt, check out the Outbound Short lines. They have the weight really moved to the front of the line, and the running line is quite thin. You can shoot your entire line easily when you need a long cast. It is an effortless endeavor, and an absolute joy to fish with.
The Xi3 can really put the wood to the fish as well. I highly recommend those rods.