I'm about to have to decide on the spec of the new kit I ordered early last year. I currently have a 310R which I love, but have always wanted to build my own (well, help to build my own anyway) so the 310 was bought second hand at the time of ordering the new one because I didn't want to wait a year. The plan all along was that the new one would be a 420R, giving me the excitement of a more powerful engine to look forward to in the new one. I went down to Crawley last Friday to drive two 420s, one a 5 speed and one a 6 speed, ostensibly to decide which gearbox I wanted to specify for my 420. Well, the gearbox choice was easy for me (6 speed, as I have in the 310, frantic but fun) but I ended up with a whole different and entirely unexpected dilemma. I loved the power of the 420, incredible, and I see why so many people love it. But I found I preferred the characteristics of the Sigma engine in the 310. Obviously now I want the characteristics I enjoy, with the power as well!! The 310 just feels more instantly responsive. The 420 feels smoother and more refined, as well as much faster, but I'm not really looking for smooth and refined in my Caterham. The 310 feels more like a racing engine. The 420 feels like a heavier flywheel (guess it will be in a bigger engine) and therefore not as responsive when you first push the loud pedal, although it seriously picks its skirts up once you get going. So I'm wondering whether I should get another 310 and look at upgrading the power (can you safely and reliably get another 20-30 bhp out of the Sigma?), or maybe I could make some changes to the Duratec engine to make it feel a bit more racy? I'm not very techy (yet!) so any thoughts gratefully received. I hope I don't upset any 420 owners by the way, it's an incredible car and I loved driving it, and I see why they are so popular. I guess I just want it all! Most use will be on the roads by the way, but with the odd track day thrown in. I know that I will find the 310 lacking power on the track, but I'm sensible enough to know I will generally find myself holding back in the 420 on the roads. The other thing is the financial aspect. Having had a quick look at second hand values, it looks to me like a 420, whilst a bigger initial outlay, holds its value much stronger. Have I got that right? Thank you all! James