How much power does the A2500.5D make?

It is rated at 4 x 60 W plus 1 x 250 W at 4 ohms, and 4 x 100 W plus 1 x 450 W at 2 ohms. The subwoofer channel is listed at 750 W at 1 ohm.

Can I run a subwoofer and four speakers off this one amp?

Yes. Channels 1-4 drive front and rear speakers and channel 5 is dedicated to the subwoofer. That is the point of the five-channel layout.

Does it work with a factory radio?

It has speaker-level inputs as well as RCA inputs, so it can take signal from a factory head unit without a separate line-output converter.

What crossover controls does it have?

Channels 1-4 have variable high-pass crossovers and channel 5 has a variable low-pass crossover. A bass EQ adds 0-12 dB at 45 Hz to the subwoofer channel.

How big is the amplifier?

The chassis measures about 17.88 by 7 by 3.5 inches, so plan a mounting spot with room for wiring on both ends.

Should I buy this or separate four-channel and mono amps?

One chassis saves space and wiring, but separate amps usually give more power per channel. Choose the A2500.5D if simplicity matters more than maximum output.