I can't help you with the Turbo Dogg review, but I do know the gap between the Alpha Dogg and the Power Dogg is HUGE, so where the Turbo Dogg falls between the two is really important. The Power Dogg is inexpensive, but you get what you pay for. The Alpha Dogg probably isn't my first choice for a $250-300 call, but it's definitely lightyears ahead of the Power Dogg. (I'm a Foxpro fan for Electronic callers).
I'd also second the other comment to try some mouth calls. You can buy about 20 mouth calls for the price of a reasonable electronic caller ($200).
Ultimately, all you really need is a mouse squeaker ($10), a rabbit distress call ($15), and a locator howler ($15) and you'll be able to call coyotes all over North America. The more experience you get, you'll find sounds that work better than others in your area, and you'll be able to find calls/brands that produce better quality sounds than others. I'd hightly recommend the Primos double reed calls (laminated wood bodies, crazy colors, but GREAT sound). On some of my favored mouth calls, I drill a hole in the bell of the call and glue in a mouse squeaker reed (buy a squeaker and cut the reed from the rubber bulb) so I can switch back and forth easily. I also tape a mouse squeaker to the forend of my rifle, so I can push the squeaker to stop a trotting coyote while I'm over the scope.
Pick up a FoxPro BlackJack or Jack in the Box, or a Mojo Critter decoy and you'll have a potent calling set up. I can't say I recommend the Quiver Critter Decoy, but it does work (really loud though).
Beyond that, I've been incredibly happy with my FoxPro Spitfire for a budget friendly model. I also have a Prairie Blaster that is amazing, but for $600, you better be serious about coyote calling before you invest. A buddy of mine got a new Flextone Echo to try out this season, sounds good so far, although we haven't hunted it yet.
The most important component of your hunt is NOT the call, it's your set up. No matter how good your call sounds, if you didn't plan for the wind well, you're screwed.