OK, You almost certainly have 126mm space between the dropouts. You can easily go to a 7 speed rear and acquire (off ebay) 7 speed brifters, preferably RSX model, but Sora if available too. In fact, you can keep your rear wheel and buy a Shimano or Shimano equivlent 7 speed freewheel. You may have to redish your wheel, but a competent bike shop should be able to do that. The nice thing about 7 speed is you don't have to spread the stays to acquire a wider spacing.
IF YOU GO TO 8/9/10 Speed, you have to force a 130mm rear wheel into a rear that's set up for 126mm. Because the stays relax when you open the Quick release, it's actually more like shoving a 130mm rear wheel into a 128mm space. YOU CAN NOT COLD SET AN ALUMINUM FRAME. But I'm currently shoving a 130mm spaced rear wheel into a 86 Nishiki Prestige. It's a little awkward and it could be interesting if I get a flat on the road, but it works.
If you like the bike, yes it's worth it. From a financial standpoint, you won't get all the money back when you sell it, but to guy that bike new with brifters will run around $800. Your call.