The current NSX gets 290 hp from 3.2 liters, which is a higher level of volumetric efficiency (90.625 hp/liter) than the 3.5 liter 300 hp engine in the RL (85.7 hp/liter). This is without the benefit of Honda's newer gimmicks like i-VTEC, improvements in cylinder head design, or using wideband oxygen sensors to allow for tighter on-the-fly regulation of air/fuel ratio.

So if you simply took a 3.5 liter engine that made the same hp/liter as the current NSX 3.2 it would have about 317 hp. If you add in all those other neat tricks that Honda does with their engines nowadays I'd say the volumetric efficiency of a new NSX motor would be even higher. Given that the original NSX was of similar volumetric efficiency to Honda's trick (at the time) four-cylinder engines, it would stand to reason that the new version would up its game to a similar level. The RSX Type-S makes 105 hp/liter; apply that to 3.5 liters and you have 368 hp. The current 2.2 liter S2000 makes about 109 hp/liter if you believe the spec sheet, but it actually makes a bit more than that. Still, apply it to 3.5 liters and you have 381 hp. The original 2.0 liter S2000 made 120 hp/liter (without the benefit of certain new tweaks like i-VTEC and wideband oxygen sensors, but with a ridiculously high redline); apply that to 3.5 liters and you have 420 hp. See where I'm headin with this?

There's no reason the next NSX couldn't compete with the likes of say, a Porsche 911 GT3. It wouldn't be up there with the 911 turbo, Ferrari F430 or Lamborghini Gallardo, but those cars would probably cost at least half-again as much as the NSX.