Well I haven't tried the PK's or the AT's. But as far as the senns and the bose are concerned, The $25 MX-500's had a fuller sound than the Bose IE, regardless of the fact that the Bose had a lot more bass, because the Bose has no high-end extension, and the MX-500 have decent highs for an earbud. (I A-B'd them at the Bose Store) They are a good all-around earbud and will sound good will all music.
However if you listen to a lot of jazz, classical or any other music where detail is important, then the MX90s are the best at $79. They have a sound signature similar to the HD-595, although on a smaller scale and the detail rivals many IEMs. If you get a chance to listen to these, definitely check them out!
But my favorite all around earbud is the B&O A8. Very pricey at $160 but the combination of great detail and good bass in proportion to their size makes them good for any music. The MX-90s have better high-end detail, but are more reserved in the low end making them not the best choice for modern music (Hip Hop, Dance). But for jazz and classical the detail and soundstage cannot be beat in a earphone this size. They are like a concert on your ears!