HP smart array P812i and storage works enclosure D2700 BAD PERFORMANCE

I have HP DL360 G6
with Smart Array P812i
and Storage Works D2700 enclosure.

Enclosure has 25x148GB 15K SAS 6G drives in RAID10 mode.
P812i has 512mb cache (50% read/50% write)

Crystal Disk mark shows ~500MB/s sequential read speed, other tests shows simmilar results.
FileCopy speed ~300MB/s read and ~500MB/s write.

I expected better results in this HW configurations, lets say 1500-2000MB/s sqeuntial read speed.

Application which runs on that HW need lots of I/O performance (sequential read) and current performance do not cover price of HW.
Can anyone tell me, is the current system performance normal, or can system be tuned for better performance and how

thanx