Ive been playing about three or four years, and have been getting by on a cheap starter guitar, until recently. The tuning isnt too good at all, i'll play for about 10-15 minutes(if that even) then need to re-tune, sometimes even multiple times in that time period,
and i dont even go near the whammy bar any more, despite there being some songs i like and want to play that require it's use.

Im willing to spend anywhere from 400 to 700(canadian) on a replacement. I play quite a variety of music, so would need something atleast somewhat versatile.
What i play the most and listen to the most though is older rock music (ac/dc, kiss, hendrix, guns n roses and etc),
and metal (metallica, iron maiden), and motley crue.

There were 3 guitars i was currently looking at, but i'm still completely open to suggestions.

Fender Standard HSS Strat


Ibanez SA 260fm


Epiphone 1966 Limited edition g-400

Go with the Fender, good middle ground for what you enjoy musically. What's the amp?
the amp is another story.
The starter guitar came with a 15 watt amp, which is now long gone.

All i have currently is a 90 watt behringer bass amp, so on top of looking for a guitar, im also going to be looking for an amp in the near future, a few paycheques down the road.
The Fender and the Ibanez are nice, with the Ibanez having hotter pickups. Both should work for you. I like the pups on Fenders, but it's a matter of preference in this case.
Both guitars are better value than the Epi imo.

If you can find one, try the Yamaha Pacifica 612V. It costs a little more than the guitars you mentioned (should be availbale within 500 US - I don't know how much that is in Canadian), but it is a bit better. It is basically a strat with an HSS configuration (Duncan JB in the bridge) and a very nice tremolo.

If you don't want the Yamaha or can't find one, the Fender and Ibanez are solid choices.