3 monitors extended display for new build on XP workstation

I need some advice on building a computer for a customer. They want to run 3 monitors (extended display, business user, not gamer). Right now they have 3 VGA monitors to use, but are willing to buy one HDMI monitor is necessary. This will be an XP Pro system (workstation).

I have been looking at the BIOSTAR TH67+ LGA 1155:

http://www.newegg.com/Product/Product.aspx?Item=N82E16813138296

(I need a LGA 1155 for my Sandy Bridge i5, but not necessarily one from Biostar.)

The video ports from above are VGA/D-Sub, DVI and HDMI.

I don't seem to understand some discussions that I've read where you can't convert a DVI to VGA and also use the VGA/D-Sub jack on two VGA monitors and the third HDMI port on an HDMI monitor.

As I understand it, I will need to get an extra display card to drive 3 monitors... at least 2 VGA and one HDMI?

I'm looking for the least expensive solution and NOT seeking best fit for future expansion.

Buying more than one monitor to replace one of the 3 VGA's is out of the question, due to the position of the employee getting approved for such purchase.

Any advice on:

1) What display card I will need?
2) Can I add a display card without disabling the internal motherboard display?
3) A better setup than the above for the best price?

Thanks in advance folks!