I just did new speakers the other day, went with Kicker CS 654's (300w max 100w RMS) as they were on a good spesh. Had to get some spacers too as even though the speakers themselves are the same size as the stock ones, the bolt holes are considerably further apart for the stock ones and the bespoke sort of surround that Hyundai have put them in.
I left the tweeters as is, I didn't want to mess with their mounting or wiring, it didn't look nearly as 'plug and play' as new woofers. Also I don't think that even the front are run as 'splits' where the signal is cut and sends separate frequencies to the woofer and tweeter (I forget the proper term for this), as when I put the new speakers in there are definitely highs coming out of all of them (did front and rear 4x speakers total).
The stock woofers that came out had a Hyundai part number and were otherwise labelled as '20w' - so the new speakers as you could imagine are a massive improvement. Oddly enough the bass doesn't seem quite as deep as the stock ones, it feels a lot more punchy and crisp, and naturally they don't distort when pushed hard like the crap paper cone stockies. I unplugged the stock ones and cut the plugs off to just crimp down onto the leads that the new speakers came with. I'd say beginning to end with all the parts in hand it will take an average person 20-30 minutes per door, including trim removal and re-installation and everything between.
Very happy with the end result, the sound is a lot more clear and punchy and just seems to get better the louder it is pushed, a great result for a stock head unit. It really fills the cabin with the right frequencies a lot ... fuller I guess and makes the sound system really respectable, especially considering they are run without an external amp.
next up I'm planning a small under seat self contained subwoofer and amp combo, thinking this guy - NEW PIONEER TS-WX120A OVERSIZE 8" SLIM SUBWOOFER SUB INBUILT AMP UTE TSWX120A
my question there would be how hard is that install going to be? I know I'll need to run wire all the way to the battery, but does anyone also know if the stock head unit has the right outputs ready to go or if some splicing/modding is needed?