You're making this WAY too difficult. It's really not worth investing TOO much in your system, it' simply not that good...I suggest you don't "waste" your money on an AIW card. Take the time to read the info at the following sites.
At the MSI website, here's what it says about your AGP slot:
• One AGP (Accelerated Graphics Port) slot.
- AGP specification compliant.
- Supports AGP 2.0 2x/4x
http://www.msi.com.tw/program/products/mainboard/mbd/pro_mbd_detail.php?UID=411
OK, so now that you know your board supports AGP 2.0, you can read this:
"The keying for AGP 3.0 cards is identical to that of AGP 2.0 cards to retain backward compatibility. A motherboard that supports 8x AGP should work fine with a 1.5V (AGP 4x video card), and a motherboard that supports 1.5V (AGP 4x) video cards should work ok with a .8V video card (AGP 8x), however in the later example the video card would only work at the fastest speed the motherboard supports (AGP 4x)."
http://www.directron.com/15agpguide.html
In other words, an 8X AGP card will work on your 4X AGP board, but it will only be able to run at 4X speed.
Now here's a few cards to consider...I threw in the AIW since you mentioned it, but IMO, it's not worth the extra $80-100 unless you really want/need the added features. Keep in mind that you can get a PCI TV tuner card for less than $30.
9600Pro for about $70:
http://www.newegg.com/Product/Product.asp?Item=N82E16814102409
9600XT for about $90:
http://www.newegg.com/Product/Product.asp?Item=N82E16814102510
AIW 9600XT for about $170:
http://www.newegg.com/Product/Product.asp?Item=N82E16814102352
This space for rent