Pyle and Bose are both very poor companies when it comes to sound quality.
The wattage rating is the limit that the speaker can tolerate before becoming damaged.
Peak wattage is a rating of short bursts of high power, whereas RMS is a rating of continuous power.
A speaker can always work off of less wattage, but they may not be efficient enough for very low wattages. (will sound muddy) Also an amp rated to put out a certain wattage won't put out that wattage at lower volumes. So it is possible to connect a 100w speaker to a 150w amp so long as you don't crank the volume and overpower the speaker.
As far as speaker recommendations, I'd be very inclined to go with the polk db line. Because you're looking to keep the Delco radio, your going to need some fairly efficient speakers and Polk'* dB line is really hard to beat in that department.
Here'* the crutchfield listing for the db690'* (for reviews and info): click here
soniceletronix has them priced for less: click here