your architectural programs will probably appreciate the extra power of the i7, one way to cut down your prices a bit may be using the P7P55D motherboard and an i7 860, it will performance as well and reduce your costs a bit. Depending on how often you use your architectural software, and if its 64 bit, you may want to opt for 8GB of ram if you do an LGA 1156 build, if its only 32 bit there is no need for extra ram since it cant use more than 2GB anyway, if you do stick with the 920 the 6GB of ram will be plenty even if it is a 64 bit program.
How about this?
Intel Core i7 860
Asus P7P55D Pro
DDR3 8gb (4x2gb) G.Skill Ripjaws 1600mHz (4GBRM)
Samsung 1TB F3 SATA II 7200RPM 32M
Sapphire HD5850 1G GDDR5 PCIE 2D HDMI
Antec Nine Hundred 2 Black Case (No PS)
LiteON IHAS324 SATA DVD-RW 24X Black
LG W2253TQ-PF Gloss Blk 2ms
D-Link DWA-547 RangeBooster N650 Wireless LAN PCI Adapter
Logitech Deluxe 250 Desktop USB
Logitech X-140 2.0 Speakers System