Your work so far is very good, but it's just not quite there yet. The idea and the layout are for the most part fine.
Please listen to what has been said about white space and the text, as-well as balancing the items on the page. Don't be afraid of spreading it out a little. Also consider a different font - I agree with you about the blue/green however that font is too stressing on the eyes to read with a dark background.
As an example the comparison page is very cramped, there's no room between the title and the table, and the table is a massive block of information that's hard to digest. Take a look at the list of items
here. What do you notice, are there any table lines? What about the use of indentation and font styles? Are the headings seperated from the items? Basically, look at what you consider to be good layouts and ask yourself what makes them good.
You could reduce the weight of the table with a paragraph saying 'All models feature 8 air bags, tyre pressure monitoring... ...as standard'. Then the table can be used to highlight why the supercharged is that much better than the base model - to convince people to buy the better one. It will also give you a lot more room to play with.
At the moment it's good. With a few minor alterations it could be excellent. Once again, please take the advice that's been offered so far - after all, these people do it for a living
AppleMatt
edit: Also I'd consider changing the 'Quick Specs' title to something a little more professional such as 'Model Overview' etc etc