For the 05-09 GT's, the steering pump pulley acts to handle the allowed amount of fore and aft play in the belt (they're also a culprit of many problems as the PS pumps are made of stupid). Anyway, point being that pulley should wiggle (in and out) a little. None of the pulleys should have a shaft wobble though. (God this is a nutty conversation...)
If you haven't replaced the belt, do so. Not worth trying to keep, they're cheap and you can rule out several issues just by doing that.
Belt tensioner won't last forever, too, but check that it moves freely with consistent oomfph on a normal breaker bar. They're cheap, too, so again, good part to replace and super easy, too.
The idler pulleys can go bad. They're a little more expensive to replace, but a great value upgrade would be the idler pulleys from Steeda (they look good, run much better, and are rebuildable). I think they're about $120.
If your water pump was bad, you'd probably know it by other problems (noise, cooling problems, etc). The pulley should have no play in it at all and should be easily turnable by hand, but shouldn't go free-spinning like a fidget toy. There's 4 bolts on the pulley. Give them a check-over to make sure they're tight (spec is 18 ft/lbs).
Testing the AC pump pulley is trickier. With no power it should freely spin as the clutch isn't engaged. Shouldn't be any play in it, though. Testing if there's an issue while engaged is easily done by running the car with the AC system all turned off and going for a drive. It should never engage the clutch if there's no demand for AC, and you can see if the vibration happens.
Another culprit that pops up on older cars is the alternator pulley. If you have any doubts about it, just replace the alternator. It'll probably be due for one anyway. Little more expensive a fix, but it's one of those "many things reliant" parts that you can't hurt yourself refreshing.
Crankshaft pulley? Eh, Check that it feels solid. There's actually a rubber damper in it but you'd have to be experiencing other issues for that to be bad (for one the whole engine would be upset all the time, not just at speed).
Vibration from the front can come from other sources, too. I'm assuming at "top end" you're experiencing this while out moving around, so you could have suspension issues (worn ball joints come to mind). Check all the mounts (and motor mounts) are good.
As for electrical...There's a decent parasitic draw for the security package when the car gets alerted to movement or anything is activated (door unluck, trunk, lights, etc.). It goes away (well, mostly) when the system goes back to sleep, but if you keep the car outside or any place where things move around the car (active garage for example) it could spin up a lot and cause a drain.
Clean your MAF (with MAF cleaner...not something else) and clean the throttle body (DO NOT USE CARB CLEANER...only use electric throttle body cleaner).
Also check your air filter. If it came with the car, consider it bad and replace it. (Another cheap solution to avoid headaches.)