From what I've heard, no, the non 5.1 cards cannot be converted into 5.1 cards. What do you plan on doing with the card? I mainly bought it for the Optical out ability so I could record onto my MD... of course, the front jacks for the headphones and mic are also good to have. The normal Platinum which includes the Live! Drive I is a pretty bad deal... of course, if you can find it for $100 (Best Buy and CompUSA sold it around that price when the 5.1's came out), it's an ok deal.
I don't think there's really much of a price difference between the normal Live! card and the Live! 5.1 card... so if you had the chance, grab the 5.1 card. Then again, you could also pick up the X-Gamer for around $50 after coupon and free shipping from Staples. Think the $25 off coupon expired yesterday, the $20 off coupon is still around. The X-Gamer basically gives you a bunch of pretty good games. The Live! Mp3 gives you some Mp3 software and the Platinum 5.1 basically gives you both software bundles and the Live!Drive IR.
The Live!Drive IR includes Optical in/out ports, RCA auxiliary in ports, IR and remote, Midi in and out, line in/mic, line out (headphone) and S/PDIF in/out. So... aren't Midi in/out ports for the keyboards? I was under the impression that they were... if I'm right, then I think Lore made a mistake.
Finally... if I had to buy it all over again, would I? I'm not sure... the Optical out and headphone out and mic in ports on the Live!Drive IR are the only real ports I use on that thing. I don't even play the games it came with, which to some people might be worth it to buy alone. Unreal Tournament, Thief, Deux... and a couple of more, don't remember. I would have probably just picked up a Hoontech Optical daughter card.
Up to you to decide if the Live!Drive IR and 5.1 ability is worth the extra $100-$150... depending on how much you pay for it.