If you want to put things in your signature, the most often used stat (and thus most easily recognizable and comparable) is
horsepower per tonne or HP/tonne. (That's a "metric ton" not a US ton, so 2,204.6 lbs. or 1,000 kg)
This is how Caterhams are named actually. They are called the CSR 260, R300, R400 and R500 having 260, 300, 400 and 500 HP per tonne respectively. The car weighs approx. 1,100 lbs. (500 kg or 1/2 ton) and for example the CSR 260 has 130 HP. At the other end of the spectrum the R500 has 250 HP.
130/0.5 = 260 HP/tonne
250/0.5 = 500 HP/tonne
Pounds per HP or HP per pound is much less commonly used.
Mine weighed 2,492 lbs. at the convention (1.13 tonnes) and has 303 WHP so that gives me 303/1.13 ≈ 268 WHP/tonne. I don't usually like to do this, but you'll probably want to convert from WHP to HP if you want to compare to OEM vehicles.
303 * 1.15 ≈ 348 HP
348/1.13 ≈
308 HP/tonne for my car.
That's comparable to a Caterham R300 (sort of) for whatever that's worth.
For a long time 500 HP/tonne was the holy grail of performance cars after WWII. Some time in the change of the century with the power wars going on, someone got the crazy idea to make a car with 1,000 HP/tonne. That car is the
Caparo T1 and re-wrote the book on performance cars with 1,045 HP/tonne.
For reference the Ariel Atom weighs 456 kg (1,005 lbs.) so similar the Caterham, about 250 HP gets you to the old pinnacle of 500 HP/tonne. The upcoming 500 HP Atom should put it slightly past the Caparo T1 at 1,096 HP/tonne.
The
DP1 is 375 HP and 850 lbs. (385.5 kg) so 973 HP/tonne.