Not to be the bearer of bad news, but we've seen customers use the Sun CoolThreads servers and each had performance issues (Sam actually used to work for one of them). While the servers tend to do well at low-computational, high thread applications, OTM is highly intensive and benefits from strong, number-crunching CPU cores.
I'd recommend running the VolanoMark and DaCapo benchmarks using the Sun 1.4.2_12 JDK to better understand the performance limitations of this platform:
--Chris