Everyone's favorite eBay seller TZD almost always has PCE controllers for $40 shipped. PCE is the way to go. Lots of colors to choose from. 2 button. 3 button. 6 button. Take your pick.
You can get MUCH cheaper but hey, at least he's in US (assuming you're in US), so your controller won't get stuck at a port for a month (never happened to me, but others have said its happened to them. I buy from Japan a decent amount).
https://www.ebay.com/ulk/itm/321755364362
How are the Avenue 3 controllers? Neat feature on those is you can have quick access to the Select button which can be useful and I hear they can also be used for "slow motion" effect on some games. I'm mostly single player though I have a friend that comes ever so often, but regardless, I might as well have a bit of an arsenal of options at my disposal for whatever occasion. I've pretty much accepted the fact that I'm not going to pay less that $30 or so for a decent controller although I like the feel of the classic Turbo. It seems just a year ago the classic large DIN Turbo controllers were only $20 online.
Console5 sells some pretty nice controller extensions for a variety of consoles, NES, SNES, 15-pin (Famicom/NeoGeo/5200), 9-pin (Atari/Sega) as well as Turbo converters.
http://console5.com/store/turbografx-turbo-pad-to-turboduo-pc-engine-console-controller-adapter-cable-1.htmlhttp://console5.com/store/turbografx-turbo-pad-to-turboduo-pc-engine-console-controller-adapter-cable.htmlAs for Turbografx versus PC Engine, I've got a standard bulky Turbografx that's reliable (I just did the logo backlight mod yesterday afternoon and it's awesome), I know how to search for both on eBay, et al and most sellers use both terms regardless of which region the hardware is. I've got my PC Henshin adapter and Everdrive that have more than paid for themselves already. Hucard/Turbochip games are a luxury but nothing quite like owning an original. If prices continue to inflate, I may even sell off a couple US games to recoup my investment.
And CD games are off the radar for the foreseeable future, though if I ever get some disposable income, I might invest someday invest in a PC Engine "Briefcase" setup.