I'm a big Porsche fan, but more towards the Cayman S model...kind of right in the middle of all of them. Anyway, I don't think you're comparing apples to apples.... I think if you bought the Z to be a straight line beast, you bought the wrong car. While 300 + RWHP isn't too bad, my pontiac solstice was pushing that to the ground and did 0-6 in under 5 seconds. Now thats a power to weight issue too but after around 80 MPH, its not going to contend with a big V8 or muscle car. Put it into the turns and most V8s wont see anything but its tail lights. The Porsche is a great car and each has its own purpose. After having the Z for a few months now, it's definately designed for carving up the curves.
Its a purpose built car. I bought mine as a daily driver, so I made no mistake that this was going to be a canyon carver for the daily grind and not a weekend trailer queen. And for the $, I think it's pretty refined; campared to my previous Pontiac Solstice GXP. There are a lot of great cars on the road to choose from. Perhapse look at getting a used Porsche for the weekend rides or something?