Anyway, are you sure you want to cook three times a day? These days I don't do much more than heat water in the morning for coffee or hot chocolate, eating breakfast bars and dried fruit. I don't cook at all mid-day. Then I'll heat some water in the afternoon and evening for the aforementioned coffee, then maybe some freeze-dried soup and a freeze-dried meal .
As for a stove, your old Optimus should work fine. The Simmerlite ($90; www.msrcorp.com) would be a nice upgrade, thoughit's one of MSR's newest stoves, a liquid-fuel model designed to cut weight while offering good flame control. Fuel consumption is one pint per 77 minutes at full flame, which translates pretty well into the half-pint-per-day notion; running it for 30 to 35 minutes should provide more than enough cooking power no matter what you're doing.
The Sierra stove from ZZ Manufacturing ($57; www.zzstove.com) is a bit more problematic. As most readers know, it's a wood-burner that uses a small battery-powered fan to stoke the flames. From most reports it works pretty well, although it's not as fast as a gas stove such as the Simmerlite. Tends to get a little dirty and sooty, but that's surmountable by carrying a small sack to put it in while you're hiking. You also need to tend it a bit to make sure it stays fueled. But, on the other hand, there's no fuel-weight penaltyyou just pick up small bits of wood around your camp and use that. I'm rather neutral on it, though for some campers it's great.
Anyway, hope that helps clarify things, and hope you have a good trip!