Not sure why weird stuff and information has been showing up in this thread lately.
Thank you Pinash for the good info.
Kicker CS series are your best choice for back box speakers. The Kenwoods are horrible. (go back several pages to see the speaker fight reviews) If you are afraid of seing the yellow come through the foam(you most likely won't) then use a black sharpie to go over the yellow accent - poof all better. I do this with the chrome accent on the Alpines.
The Boss subwoofers are NOT a favorite swap. I have no idea where this even comes from. The Boss has not even been discussed in this thread with the exception of a brief post I made a few pages back about it - AND I have not rated it as it's still sitting on my table waiting for an install to test. #2 whoever said they have used them, they didn't need a spacer and you only needed to push down a bit to get the screws to fit AND they sounded just "ok"... Well, problem #1 is they DO require a spacer(see my post a page back). The cabinet cut out is too small, and the Boss gasket is too small to mount properly. The front speaker suspension is literally being squished against the edge of the cabinet cutout and most likely the plastic mesh if you didnt remove it. Which brings to point #2 and most likely the cause of your just "ok" rating. Add a spacer and see if it improves. (Again, i have not reviewed the Boss, so they may very well be just "ok" if and when mounted properly)
Using speaker "adapters" is just fine for converting from 4" to 5.25" speakers, you do not need new plates for this. I would only recomend new plates if you were buying speaker lights at the same time, because of the discount and ease when doing it all at once. BUT if you are not planning speaker lights, then the plates are not nescessary. Two points here: #1 yes there is a stock cutout for a 4" round, however; the cutout is plenty big enough to let all the sound out that is produced from a 5.25" speaker. Don't over think this until you see it yourself. #2 depending on what speakers you want to install you may need a spacer of some sort, even when using new plates, to provide room for the tweater. Soooo... The adapter alone would be the spacer and new plates would not be needed(just added expense)
Pricing - it is sometimes hard to watch when decisions are being made based on pricing alone. Don't get me wrong, I started this as a DIY thread and absolutley encourage everyone who is tinkering with the rest of us to try out all kinds of things regardless of price. That's the point of tinkering.... But please don't let price be your motivating factor if you don't have the tinkering mindset and you are here to do a solid upgrade. Spend the couple dollars and get the proven good stuff and be done, these are $7k machines at the low end, an extra $20-$50 shouldn't be the decisive factor. Even using the best stuff listed in this thread you will still spend less money and get a significantly better result than more expensive plug and play options available.
Whenever I have guests over, and they hear what some of these installs sound like in person they are blown away. It truly is amazing what can be done with just the info gathered by everyone in this thread.
Lets keep the thread and its readers heading forward on solid ground - without diverting recent visitors off the side of the road and into the mudd.