Overkill upgrade?

12GB SQL 2005 Database, growing 2MB/day. Currently running on x32 Windows 2003 Enterprise in a Cluster between Two Dell PowerEdge 6850s and with a directly attached, fully populated PowerVault 220T.
Now this configuration is s l o w, mainly due to write caching being disabled on the Perc4 cards (required for the cluster).
So, I was given a budget of $40k to try and speed things up.
This was my new solution, What do you folks think?
Replace a 6850 with a PowerEdge 2950 with 2x Quad Core Intel Processors, 8GB RAM. 2x Dual Port MD3000 HBAs (4 connectors)

Attached to the 2950, a dell MD3000 Storage array, fully populated with 73GB 15k SAS drives.
which is attached to a MD1000 array, fully populated with 73GB 15k SAS Drives.
which is again attached to another MD1000 array, with 12x 73GB Drives and 3x 750GB SATA.
Here's my thinking on the layout of the database :
MD3000 - 14 drives in RAID-10 for the production MDF data files + 1 hot spare
MD1000 - 6 drives in RAID-10 for database online logs + 8 drives in RAID-10 for tempdb (we have lots of bad programmers) + 1 hot spare
MD1000 - 7 drives in RAID-10 for fileshare (which contains files previously shared by the cluster) + 4 drives RAID-10 for non-prod dbs + 1 hot spare + the three 750GB fatties to hold Data and Transaction log backups.

Steven Vallarian