JD NC

OK, having gone down the car audio rabbit-hole (footwell subs! rear panel speakers!) over the last couple days, I think I've come full circle on my desired setup.

First upgrade:
Alpine 133BT and Modifry DCI are already installed.
Replace OEM speakers with Polk DB651s ($60) - fits the stock baskets, and the coaxial design makes the install less complicated and puts the tweeters in a better location. Big drawback is that they have a weaker low end because they're so shallow, but I can live with that in the short term. If my OEMs weren't shot and I could wait, I would probably save up for something better, but these are cheap enough that I can get them now and at least get my stereo back. They're also cheap enough that I can toss them for something better down the road after I have the rest of my system ramped up.

Next:
Sound Ordinance B-8PT ($150) - slim powered sub, fits under or behind the seat, accepts high level inputs from channels 3 and 4 of the HU, and should compensate nicely for the lack of low end in the Polks. I had been wary of getting a sub, since it's so easier to go overboard, but this seems like a good way to fill out the low end without extensive modifications. This is definitely a Crutchfield purchase, since I'll want a step by step to tap into the vehicle's power. Still, this will be the simplest type of sub install by far, and allows for a very easy conversion back to stock.

Next:
Alpine KTP-445 power pack ($130-150) - plug and play amp, gives the Polks some extra headroom, and since the sub is self-powered, don't have to worry about underpowering the sub.

Thanks again for all the input!

oth

I have to say, I don't love the idea of using coaxes if you already have a spot for a separate tweeter -
while there are some theoretical benefits to closely aligning the woofer and tweeter, in the case of
the s2000, the occupants' legs tend to block the lower-door position, which drastically affects higher
frequencies. Early cars (through '01) had coaxes, and the separate tweeter introduced in '02 was
definitely an upgrade.

XtC-604

The tweeter location is ideal in the 02+, if you get a nice set of components, they will and do sound phenomenal.
I'm using a premier series pioneer HU, with some PRE-2005 Alpine Type R components with a JL W3 Sub in the trunk, all powered by a 600W Pioneer Amp. I'm pretty happy, but i'm thinking of upping my game just a little bit!

JD NC

Finally pulled the trigger - Polk db6501s and Alpine KTP-445U are on their way.

I tested the coax and component Polk DXi models (which are same as the db models with different grilles) at best buy and both sounded really good for my needs. I didn't hear much of a difference between the two, but the listening environment at the store was wretched so I couldn't draw any real conclusions except both seem to outperform the other speakers on display. I went back and forth but finally settled the component set of Polk db6501s for $105 at amazon. Even though I didn't hear much difference, many reviews of the 6501 say that the bass response is a little better than the 651, so I don't think the extra $50 is much of a gamble. I'm also less worried about being overpowered by the treble than I was initially. The crossovers on the components are configurable, and my HU has a 3 band equalizer, so I'd much rather have too much treble that can be trimmed than too little bass and midrange.

I had steered clear of the 445U because it wasn't plug and play like the 445, but I found that a big advantage of the 445U over the 445 is that the 445u is bridgeable out of the box to 2 channels x 90W. The 445 can be bridged as well, but it's not simple and voids your warranty. Since I'm unlikely to get rears anytime soon, having 90Wx2 out of the gate is really nice. On top of all that, I found the 445U for about $25 cheaper than the 445.

Thanks for all the advice, everyone! Will post pics of my setup when I'm done.

JD NC

Installed everything last night, and really happy with the setup.

The db6501 tweeters are definitely on the bright side, even with the crossovers cutting the tweeters by -3dB. Interestingly, it's only a problem at medium volume. Low volume sounds great, and once I get it nice and loud, the mid and bass fills in a bit. I turned down the treble and midrange and upped the bass on my HU, and that has been working nicely so far.

As expected, I'll need a sub to get real bass, but the bass response on the Polks is surprisingly good. What they lack in power, they make up for in clarity. Big upgrade over the stock speakers, especially with the 445U supplying 90W/channel. Now that I've had a taste of quality music in my car, though, I'll probably be itching for a sub sooner rather than later.