yes it would be good to hear other gear. I would love to hear your Grados and my T1 on your graham slee. The thing is my Wa2 is a high impedance amp so i don't think it would sound too good with the Grados considering they are 32 ohm's.
does the graham slee have an option for pre-amp? the WA2 is a great pre amp. It would be interesting to hear the WA2 and Slee together if that was possible.
The T1s work well with the Graham Slee, but the Grados (and I guess lots of other headphones, too) are where the Graham Slee really shines. See more on Graham Slee/Grado PS1000 partnership in this review. It makes for nice reading and is one of the reasons I chose the Graham Slee.
I noticed on the Woo Audio site here that the WA2 is recommended as an able partner with the Grado PS1000. Cooooool!
Not 100% sure if the Graham Slee and Woo could team up, but I would email Graham Slee and ask them closer to the event. There is a page on their site (see the 'features' tab here) that appears to indicate the amp can be fed off a pre-amp.
If we can make an event happen, this could be fun!