I don't know WHY this hasn't been mentioned yet, but the Ariel Atom seems like it would be a reasonably good choice in this situation. that, or really any of the Superlight series cars that RCR makes, especially the Nemesis, and you can't really leave Ultima out of the equation either. also, might be worthwhile to see about a Radical, and the Riley Track Day Car sounds like a damn good choice as well, and if you've got oodles of money and want to have the potential to outrun a Benneton Ford or maybe Aryton Senna's McLaren-Honda, POSSIBLY a Caparo T1 with an extra set of wheels shod in race slicks, the latter three being more or less money-is-no-issue (the RCR kits actually seem to be reasonably cost effective, for what they are)
now, within the realm of what a Lotus would go for, you can get yourself some seriously quick cars and still have a reasonable chunk of change left over for some extra underwear that you'll almost certainly need after getting to the limit in what might just end up being an engine with wheels. Exige money will get you an Atom, and throw the 300bhp supercharged engine, Alcon track brakes on and the CF wing kit on it and most anything under $100,000 will have at least slight difficulties keeping up with you. if you were so inclined and didn't mind the lack of wings or a passenger seat, the RCR Superlight Nemesis plus the most powerful sport bike engine you could find would be a VERY potent combo and would likely fall under the $40K mark, possibly under $35K if you were lucky. not a whole lot of protection for the wheels, but that would also be true of the Atom or a Caterham, and of the three the Nemesis seems to offer the best protection for the driver
