I don't know about the buttons and sticks, I would go with what was said above about that...
I bought the x-arcade DIY harness:
http://www.xgaming.com/byoarcade.shtml20 buttons + 2 joysticks worth of inputs, as well as all the wiring you need for all of them, pre-assembled for $50? The time savings alone were worth the extra $25 or so you end up paying over buying a different encoder, honestly... plus it's keyboard programmable with a hardware switch (no program to fiddle with, just plug a keyboard into it, press buttons, watch the LED, press more buttons, etc)
I have both this and a JPAC in my machine currently. I use the X-Arcade harness for all player sticks and buttons, and the JPAC for all my extra buttons (coins, flippers even though x-arcade has them, I dunno - I'm psycho, interface buttons)... but also use both to keep my wiring seperate (so I can rip off my CP top and make other ones if I ever get the itch to do so, and keep all my interface buttons on the cab... if that makes sense)
Anyway, long story short... if you're going to get *anything* from X-Arcade, the DIY kit from them and buttons/microswitches/joysticks from Happ makes for a spot on arcade-perfect experience.
I play SFA3 and SF3 (as well as all the older versions of SF games) and a little bit of KOF on this setup as well as in real arcades, and I can't tell the difference between my Happ/X-Arcade setup and the actual SVC Chaos setup. I can tell a difference between it and classic, old-school SF2, but it's not negative at all, and so minute that I can't put it into words right now without both controlsets in front of me. I can throw dragon uppercuts (F,D,DF P) on SVC chaos much better than on SF Alpha 3 in the arcade, but on my home setup I actually feel equally comfortable in both.
That's about the best I can sum it up with my mileage. I have not used X-Arcade controllers and buttons. hope that helps.