Paul brings up a couple of good points that might be looked at in a slightly different way:
Balance is everything!
By that, I mean:
1. That a well-thought-out engine with balanced (or application matched) components will probably give you what you want AND run reliably, too. For example, my 2,110 is running carburetors, a cam and an extractor exhaust system that I took the time to learn the specs of ahead of time so that they would all "play" together (basically, flow the right amount of air through with no bottlenecks). All this gives me a torque band that comes on at about 2,500 RPM and lasts to over 5,000 (really strong above 4K). Right what I wanted. Makes a big difference. If I were to run larger displacement I would have to go through the study again to select other components that would all flow together. Guys like Jake and Pat Downs make a living testing and running a lot of different stuff together and usually know what plays with what, reliably. Talk to them.
2. The gear ratios I chose, while maybe not "perfect" in some people's eyes, are matched to both the engine and how I tend to drive it: I never drop below 2,000 rpm, prefer to stay between 3,000 and 4,500 and have no problem cruising around town all day at 3,000 (some neighbors like it, some don't). My ratios also help to effortlessly keep it above 3,000 all the time, regardless of driving conditions, pushing the proper amount of air through the fan and keeping the engine cool. Lastly, I told the tranny builder I wanted something for about 200+ HP. If I were running a 2332 or a type 4 I would certainly get a beefier transmission with far more rugged mounts and run Porsche 930 CV joints just as a safety factor.
3. I'm running disk brakes up front, drums rear. They seem to stop well and can haul me down from 105+mph to 40mph in a little less than 150 yards (although I haven't tested how many times in rapid succession I could do this ;>) That's good enough for me and what I want to do with the car, but if I were to run a larger engine, I would probably convert the rear to disks, just for that much more stopping power (and probably add a remote brake booster as well - Simon Hambley did that on his car).
4. I'm running BIG tires (205X16 and 225X16) that stick like Locktite. I have yet to get the rear to break loose on a road course, but I probably wouldn't push it as hard as an SCCA racer. I can feel the shift when the sidewalls bend, but that's as far as it goes. Those might be adequate for more power, but something a little wider might be called for.
5. I have 3/4" anti-sway bars (front and rear) and an IRS rear end. The IRS is fine for more HP (I personally would not run swing axles on higher hp engines, but that's just me) but I would probably bump the rear anti-sway bar up to 1-1/8" or so, just to keep the tires flat to the road in harder cornering.
The point is, my car is balanced; The engine output is matched by the rest of the car to give you a whole concept. Many people drive Porsche Boxsters and (except for the "S" version) their first impression is that the car is slightly underpowered. I've driven Boxsters at New Hampshire International Speedway on the road course, at speed, and a non-"S" Boxster is a formidably fast car for the displacement because it all works together. The harder you push it, the better it feels and, while it won't quite keep up with a "Spec Miata" race car, it was pretty darn close.
I think that there's a lot more to the equation than just getting more horsepower. As Paul said; you might get a car that's wicked fast in a straight line or can snap your neck on shifts, only to fall back in the pack when you hit the twisties cuz it can't keep up. I know you've been upgrading some parts of your car already, so maybe this will give you a little more to ponder....
gn