20 whp isn't bad, it's a very noticeable gain. We get spoiled by the ease of making power with a turbo car, but I remember back in the day when I had my accord I bought a 30 dollar ebay intake and by golly that >5hp increase made the car a lot more fun especially considering the money I spent. I was about to buy a dc sports header and get a 2.25 or 2.5 inch exhaust which together would likely have given me less than 10-15 whp, and then do a 75 shot wet nitrous kit, but my parents told me I couldn't get the nitrous, and that's when I decided I was getting another car.

Anyway, back on topic, all of those things sound like good ways to get a little extra pep. If you like the car and just want a little bit more acceleration then go for it. If you really want to go fast, I'd look for another platform to work with.

*Edit* I'm not so sure about the cutout. On a naturally aspirated car, an exhaust can actually make power. Put the right size exhaust on there and it can help scavenge exhaust gas and make more power. Too big or too small and you'll lose low-end torque, though you might pick up a little hp at the top end. The cutout might be ok for a little bit extra at the track, but on the street it would kill his torque and be ungodly loud. That is if what I remember from those aforementioned honda days is correct. Now if he had a turbo car, I'd be all for it, in fact my plan is to use a stock exhaust and have a 3" electric cutout right after the o2 housing with a dump tube to get the exhaust mostly out of the engine bay. Can't argue with the gains there, and open o2 sounds sweet... when you're in the mood for that kind of thing.