Cheers, it is great to have it all sounding a lot better. In total for installing just the audio, I think probably about 4 hours. It's the first time I've done it ever, let alone in a small car like the Clio. That includes running the sub power cable through the firewall which took me over an hour as I had to do a bit of research and then trial and error with methods of getting it through! It also includes taking the entire dash top off, as I wanted to run the supplied microphone to my drivers side pillar as mentioned. It was worth the effort and actually, it was useful to have access as there's a reasonable amount of space for wires, to the right of the passenger airbag. A bit of a gap between the centre console area and the passenger airbag unit. It's not huge but it's enough to house a good amount of wires that I had taped into neat bundles.
Regards the Pioneers in general - I would consider speakers for a similar price point, but I wouldn't rule the Pioneers out now they're being supplied power and better quality audio output in the first place. They are pretty good for my tastes in a car environment. I listen to a broad spectrum of music and haven't found them lacking with anything in particular but I'm no audiophile. I already had the front speaker set, so it was more cost effective to match up with a rear pair as Goodj suggested. They're above a factory standard level (when powered by the power pack at least) and have enough punch for me. They might benefit from a little more clarity up high if you sit around with the engine off a lot.
The stalk adapter is a Connects2 CTSRN003 and deals with the display part too. You will need the Connects2 CT27AA01 antenna converter. If you're getting the same headunit as me, at least.
I'm not going to do anything with the sub remote. The headunit has a lot of options, including polarity reversal and I don't think it will look good, even if mounted/secured into the dash/cup holders or wherever. I'm also not sure if it's really needed, if the sub remembers the settings without it being plugged in I will just unplug it and put it in the glovebox. It's not as if it needs tweaking between songs. Definitely not at a level that you can't do from within the head unit in my opinion!
I think the smaller subwoofer would be a better bet and I THINK with that length, you will get it into a much nicer position under the seat, but I couldn't tell you if it'll 100% fit. I ran the wires for the sub from the back of the head unit, down behind the climate control panel and behind the power pack (which I install behind the CC panel with wires going from the left to the right and the alpine logo facing you) and then I pulled out the centre bottom of the dash completely. I ran the cables down there and on the passenger side there's some air ducts I presume for the air con etc, I ran the wires on top/next to those and under the carpet. It was a tight squeeze as I don't have tiny hands but it worked with a lot of swearing and squeezing! The power cable runs the left hand side of the passenger seat and will eventually be stowed behind the plastic trim there.
Hope that's helpful bud!