Lewis,
I used XRs on my previous bike and got folding Hurricanes for the replacement.
Having ridden them for around 1,500 miles now they have proved ideal for my riding on mostly tarmac with some off road riding, nothing too extreme though. I now use the extra light inner tubes for an extra rotating weight saving.
I have carried up to 30 Kgs of luggage and they seem to cope well. I run them quite soft for the extra comfort.
Hurricanes - definitely worth a try.
Julian.