Corsair M4 RAID0 Sloooow Write

[Fooshnik]

I had one Corsair M4, it died, had another, got the RMA back, bla bla bla RAID0. My read speeds are good, but write speeds seem to be less than half what similar configs are posting. I'm using Asus Maximus IV, Z68, have Intel RST installed, write back cache enabled. I have a similar system with a Samsung 830 installed and write speeds are more in line with what's expected. Here's what the RAID array is posting:

-----------------------------------------------------------------------
CrystalDiskMark 3.0.1 x64 (C) 2007-2010 hiyohiyo
Crystal Dew World : http://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read : 1053.089 MB/s
Sequential Write : 220.081 MB/s
Random Read 512KB : 661.452 MB/s
Random Write 512KB : 79.687 MB/s
Random Read 4KB (QD=1) : 25.231 MB/s [ 6160.0 IOPS]
Random Write 4KB (QD=1) : 41.982 MB/s [ 10249.6 IOPS]
Random Read 4KB (QD=32) : 425.502 MB/s [103882.2 IOPS]
Random Write 4KB (QD=32) : 77.662 MB/s [ 18960.6 IOPS]

Test : 1000 MB [C: 32.0% (38.1/119.2 GB)] (x1)
Date : 2012/05/25 22:34:58
OS : Windows 7 [6.1 Build 7600] (x64)

AS SSD Benchmark 1.5.3784.37609
------------------------------
Name: C_Drive
Firmware: 1.0.
Controller: iaStor
Offset: 1024 K - OK
Size: 119.24 GB
Date: 6/10/2012 11:39:48 AM
------------------------------
Sequential:
------------------------------
Read: 996.18 MB/s
Write: 204.84 MB/s
------------------------------
4K:
------------------------------
Read: 22.32 MB/s
Write: 58.05 MB/s
------------------------------
4K-64Threads:
------------------------------
Read: 415.28 MB/s
Write: 56.39 MB/s
------------------------------
Access Times:
------------------------------
Read: 0.146 ms
Write: 0.183 ms
------------------------------
Score:
------------------------------
Read: 537
Write: 135
Total: 912
------------------------------

I honestly forget all the "tweaks" I've done. Any ideas?