Do you have any direct dealings with the Sun service field engineers that come into your data centers?
Does your job's responsibilities include you sitting in for the monthly account review meetings?
Ask them !
They'll be able to pass the question up the ladder to the Sun account team that's assigned to your company.
There may even be a Sun repurchase program.
And if you can't meet with Harold... You are entitled to a trade in discount to upgrade your old Sun hardware for new Sun hardware, it's up to 25% on many systems and solutions. Or if you are just looking for cash, call some of the used hardware resellers, there are some very professional used resellers in the USA and a lot of the time these guys are looking to buy used systems.