as a system builder who deals with cutomers who want the lowest price possible and the most speed and no loyalty or love for any brand, only the brands that keep me from repairing or replaceing at a later date, my opinion based on your use, a simple MAME box.
ECS GOAL3 is (and was at one time the largest) on of the largest MB makers around. I have seen 3 of about 50 ECS boards have problems, one was user error, one was DOA and one lost a memory slot. I wouldnt hesitate to buy more ECS boards for this type of aplication, they are just fine as far as cheap boards go. I'm not a fan of Semprons so this one would be very low on my list. But as some have stated for older games it would work just fine.
Biostar, I wish i could give ya more feedback on this but I have only worked on them, not purchased. So somebody else will have to chime up on these.
ECS745- I actually had this board in a MAME box at one time, no problems at all, i gave it to a freind for a Upgrade (he was still on a athlon 1400) he uses it right now to play games (lineage II addict) and has no complaints at all. While 512 memory is probebly enough, i would go 1 gig and the old ddr400 stuff costs way more then the new stuff right now. The onboard Video is crap, but again, for your use it will be just fine, in fact with a little added memory (recomend 2 gigs) it would play some older games ok if you didnty get out of hand with the res and "gee whiz" options.
One thing to note, for my own personal use i have bought a few "open box" items from Newegg and would say i have a bad taste for there open box stuff. I have bought 2 MB's, neither worked, and 1 video Card (also didnt work), and a 15% restocking fee, or wait till another open box comes in is a NO WAY for me now.. I bought open box items that where big ticket stuff and thouhgt i was getting a deal, $350 video cards fro $50-75 off seemed good, but when you consider it ended up costing me $10 to ship back and $40 restocking fee.. not a good deal. I do know personaly people who have had no problems whatsoever with NewEgg open box stuff.
While its the most expensive one (and has a rebate) I would lean towards the 754 one.
if it was me looking for budget (and yes this would be a bit more $$) i would go:
http://www.newegg.com/Product/Product.aspx?Item=N82E16856101064 $122
http://www.newegg.com/Product/Product.aspx?Item=N82E16819116037 $67
http://www.newegg.com/Product/Product.aspx?Item=N82E16820145034 $69 ($40 rebate then $29) and there is plenty of 1gig sticks on newegg for $19 if you prefer.
Yes, its alot more $258 (-40 for rebate) but depending on case and PSU you where getting (or going to use in the original 3 boards, its not that much more).
but ya i think any of the original 3 would be fine, keep in mind memory and heatsink are needed for a couple. its so easy to start inproving when you look at makeing a budget machine.. soon that budget is out the window.
Good luck! let us know what ya do.