need a computer - what should i buy or build?

Hey,
i've been a long time sonar user and been getting along pretty well the last 10 years or so with my sony vaio RX690G 2.2 GHZ pentium 4, 512 MB PC 800 RDRM.
it's time to upgrade.
my general method of operation is to import up to 40 stereo Band In a Box wave file arrangements and then cut and paste, mix and match, and pair them down into an arrangement I can live with and then add some vocals and live instrumental performances. surprisingly I haven't had much problem with drop out as long as i use Sonar 5 and a presonus Firebox sound card.
however if i want to use Sonar 8.5 and my presonus 8 in 8 out Firestudio sound card things get dicey.
it's time to upgrade my computer.
after reading various posts here I see most suggestions are to have a machine built to specific specs. i might do that if i can find a trustworthy local builder. so I have 2 questions for the community.
1. can you suggest a off the shelf computer that will do the job?
2. if i find a builder, what specs should i specify?
looking to spend $1000 to $1500
Thanx yall
Blu

1 ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X DVD Burner - Bulk - 
OEM 
Item #: N82E16827135204 
$19.99 


1 Antec Solo Black/Silver Steel ATX Mid Tower Computer Case 
Item #: N82E16811129018 
 $99.99 

1 Western Digital Caviar Black WD1001FALS 1TB 7200 RPM SATA 
3.0Gb/s 3.5" Internal Hard Drive -Bare Drive 
Item #: N82E16822136284 
$87.99 


1 Western Digital Caviar Black WD6401AALS 640GB 7200 RPM SATA 
3.0Gb/s 3.5" Internal Hard Drive -Bare Drive 
Item #: N82E16822136319 
$64.99 


1 SAPPHIRE 100292DDR3L Radeon HD 5450 1GB 64-bit DDR3 PCI 
Express 2.1 x16 HDCP Ready Low Profile Ready Video Card 
Item #: N82E16814102882 
$64.99 


1 CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready 
CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 
Power ... 
Item #: N82E16817139006 
$139.99 


1 Arctic Silver 5 Thermal Compound - OEM 
Item #: N82E16835100007 
$9.99 


1 Mushkin Enhanced Silverline 12GB (3 x 4GB) 240-Pin DDR3 SDRAM 
DDR3 1333 (PC3 10666) Desktop Memory Model 998770 
Item #: N82E16820226096 
 $169.99 


1 GIGABYTE GA-X58A-UD3R LGA 1366 Intel X58 SATA 6Gb/s USB 3.0 
ATX Intel Motherboard 
Item #: N82E16813128423 
$209.99 


1 Intel Core i7-950 Bloomfield 3.06GHz LGA 1366 130W Quad-Core 
Processor BX80601950 
Item #: N82E16819115211 
$294.99 


1 Microsoft Windows 7 Home Premium 64-bit 1-Pack for System Builders - 
OEM 
Item #: N82E16832116754 
$99.99 


Subtotal: $1,207.89 


discuss amongst yourselves:)

timidi


1 ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X DVD Burner - Bulk - 
OEM 
Item #: N82E16827135204 
$19.99 


1 Antec Solo Black/Silver Steel ATX Mid Tower Computer Case 
Item #: N82E16811129018 
$99.99 

1 Western Digital Caviar Black WD1001FALS 1TB 7200 RPM SATA 
3.0Gb/s 3.5" Internal Hard Drive -Bare Drive 
Item #: N82E16822136284 
$87.99 


1 Western Digital Caviar Black WD6401AALS 640GB 7200 RPM SATA 
3.0Gb/s 3.5" Internal Hard Drive -Bare Drive 
Item #: N82E16822136319 
$64.99 


1 SAPPHIRE 100292DDR3L Radeon HD 5450 1GB 64-bit DDR3 PCI 
Express 2.1 x16 HDCP Ready Low Profile Ready Video Card 
Item #: N82E16814102882 
$64.99 


1 CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready 
CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 
Power ... 
Item #: N82E16817139006 
$139.99 


1 Arctic Silver 5 Thermal Compound - OEM 
Item #: N82E16835100007 
$9.99 


1 Mushkin Enhanced Silverline 12GB (3 x 4GB) 240-Pin DDR3 SDRAM 
DDR3 1333 (PC3 10666) Desktop Memory Model 998770 
Item #: N82E16820226096 
$169.99 


1 GIGABYTE GA-X58A-UD3R LGA 1366 Intel X58 SATA 6Gb/s USB 3.0 
ATX Intel Motherboard 
Item #: N82E16813128423 
$209.99 


1 Intel Core i7-950 Bloomfield 3.06GHz LGA 1366 130W Quad-Core 
Processor BX80601950 
Item #: N82E16819115211 
$294.99 


1 Microsoft Windows 7 Home Premium 64-bit 1-Pack for System Builders - 
OEM 
Item #: N82E16832116754 
$99.99 


Subtotal: $1,207.89 


discuss amongst yourselves:)

Tim - this isalmost the exact system I was thinking of building. Is it your current system, or are you considering a build?