Well, if you get a new motherboard, you need a new operating system unless you use a retail version of Windows, which very few people do. Most users have OEM editions. You're saving money by using the Q6600 though it is getting a little old. That CPU can still easily keep up though, it just runs a little hotter and is more power hungry than newer CPU's, that's all. You still haven't listed a budget so I'll make some suggestions and we can tweak things around until we reach an acceptable price point.
Motherboard:
GIGABYTE GA-EP43-UD3L LGA 775 Intel P43 ATX Intel Motherboard - A solid, inexpensive motherboard. Since you don't play games, you don't need more than a single PCI-E x16 slot. $79
RAM:
CORSAIR DOMINATOR 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 - This motherboard only allows for DDR2-1066 or 1200 memory. You can buy two if you wish since the motherboard can take 8GB of RAM, but unless you're gaming or doing video editing, you only really need one kit. Remember, you need a 64-bit operating system to use 4GB or more of RAM. $97 (Before $15 mail-in rebate)
PSU:
CORSAIR CMPSU-650TX 650W - If you want to use a newer graphics card, you will need a better power supply. Corsair comes highly recommended and with the wattage it puts out, you can run most single GPU cards with it. $99 (Before $20 mail-in rebate)
Graphics Card:
ASUS EAH5750/2DIS/1GD5 Radeon HD 5750 1GB - Since you're not playing games, there's little reason to go with a super powerful card. This card is in the latest GPU family from ATI. It has Eyefinity which makes it easier to blend multiple monitors together into one display and has plenty of ports for a simple, two-monitor hookup. $144
SSD:
Intel X25-M SSDSA2MH080G1 80GB SATA II MLC Internal Solid state disk (SSD) - Intel makes some of the best solid-state drives around. This drive should only be used to install the OS and one or two of your most frequently used applications. Note, that many SSD's are 2.5 inches not 3.5 inches which is what most drive bays require. You will need a cradle or adapter to mount this drive in such a bay. $259
Operating System:
Windows 7 Home Premium 64-bit - The Ultimate edition is a total, and I do mean total, waste of money for home users. This is the 64-bit edition required to use 4GB or more of RAM. $106