I have my 10/11 GrandSpey spooled onto a Redington AS 13/14 (the small arbor reel) and it has 230 yards of 30# backing. This reel is rated for a 14 weight line and 450 yards of 30# backing. As Fred has posted, it takes a large reel with a lot of capacity to hold these lines, and the GrandSpey uses up even a bit more space than the XLT.
I would not put the 9/10 GrandSpey on a reel rated for less than a 12 weight line and 300 or more yards of 30# backing. The XLT would be similiar. This would get you around 175 yards of 30# backing give or take 30 yards.
The 8/9 GrandSpey, which I will be using this coming summer, is going to be put on a Redington AS 11/12 (small arbor) reel that I own. this reel is rated for a 12 weight plus 350 yards of 30# backing. It would fit nicely on the Redington 9/10 (small arbor) with about 140 yards of 30# backing as Fred has already posted.
These lines take up a lot of space on a reel and they do not cast well beyond 70 to 80 feet unless you are using them on a 15 ft. or lolnger rod. They really come into their own with the longer rods. And keep in mind that unless you have learned how to cast a RIO MidSpey, SA Mastery Spey, SA Tri-Tip Spey, or double taper spey line over 85 feet, the XLT and GrandSpey will beat you up.
It is critical with both of them for long casting to have the "D" loop formed properly and that you are also able to keep 90 feet of belly aerialized, or else you are going to be very disappointed and frustrated. These lines really are for advanced spey casters. And I love my 10/11 GrandSpey' but I am fully aware that it is not for everyone. In fact, I would never recommend a person using one of these lines unless he has been spey casting for several years.