There's so many options for speakers it's hard to give you a place to start. You can typically get much higher quality drivers at a more affordable price by buying individual components. If you'd rather stick with a passive set and ditch the crossovers that will work as well. SB Acoustics, Silver Flute, Peerless, and more makes great affordable 6.5" mids. Vifa, SEAS, LPG and others offer a broad variety of tweets.
"what is a good DSP for connecting to factory radio and improving that signal quality. Also need full Xover and eq adjustments. Only need 5 channels."
Any processor that accepts high-level inputs should work. If your factory system utilizes a crossover network that sends a different frequency spectrum to each speaker you will need to make sure the signals can be internally summed to make sure you start off with a flat signal.
"when putting tweeters on active, how do you control the power going to them? I'm afraid of toasting the tweets if I hook 100watts to them."
You can use the gain on the amp to decrease volume to match the mids. You can also do this inside the DSP software (with the exception of the JBL MS8) by controlling the individual volume of each driver. It's also worth considering that the audible spectrum that the tweeters reproduce is usually less than 10% of the material you are listening to, so there won't be much power going to the tweets even with the gain up on the amps - this is the nature of music and is independent of theoretical power or gain settings. I always, always put a capacitor in series with the tweeters around an octave below wherever I plan to cross them over as a passive back-up in case I accidentally screw up the crossover digitally while fiddling with the DSP settings. For a 4ohm tweeter you can use about a 20uF cap, for an 8ohm tweeter use about a 10uF cap. That will give you a 6dB/oct passive filter at around 2khz. Always use bipolar (non directional) caps.