I'd go ahead and try out all that you are interested in and see what fits you best. I went with the Guardian myself, this was an upgrade from a '04 Bowtech Stalker (entry level bow). As far as speed, we chrono'ed mine once it was set up at 305 FPS @ 70 lbs and that is with my stubby arm draw of 26". That's smokin for my draw length so I'm more than happy.
As far as the x-force challenge if you can get that type speed out of any bow once it is set up with sights, arrow rest, string leeches, etch....the proof is in the pudding when you shoot it. As far as the decibel challenge with it...all of the bows shot Hoyt, Matthews, Bowtech, and PSE are all incredibly quiet. With only a 2.1 decibel difference between the quietest and loudest bows tested...it's really a wash -- 2 decibels is a minimal difference and less than one tenth of a decibel is EXTREMELY minimal.
If you find a deal on one of the four bows tested and it fits you well then take it, I don't think you would lose with any of these bows as long as they shoot well for you personally. That said I'd always try the bow before buying.