Want to add amplifier to previous 2.1 stereo system

I have a 2.1 audio system of rated 40 watts,
20w subwoofer + 20 watts satelite ( 10w+10w), its a generic system, these satelite are single driver satelite, and am planning to add tweeters to both of them with a passive corssover,

Satelite drivers are 10w 4ohm each.
rated Output voltage 12.5v and current 1.2A
assuming tweeter i wanna add are 30w and 4 ohm.

1.) How much load will one crossover be putting on 1 channel and how much will be the effective impedance ( i assume 2ohms)

2.) should i use previous stereo system 10w satellite speakers output as input for second amplifier I'll need to power the set-up?
 
1) Since the satellite and a tweeter operate in different frequency bands, the net effective impedance would be more or less the same as before.

2) No, no, for a passive crossover, you do not need a second amplifier at all. Instead, just feed the crossover from the amplifier outputs to run the satellites and tweeters.

Since the net power of the system should not change a lot due to the tweeters, the existing amplifier maybe retained.
 
1) Since the satellite and a tweeter operate in different frequency bands, the net effective impedance would be more or less the same as before.

2) No, no, for a passive crossover, you do not need a second amplifier at all. Instead, just feed the crossover from the amplifier outputs to run the satellites and tweeters.

Since the net power of the system should not change a lot due to the tweeters, the existing amplifier maybe retained.
Okay, what you say seems to make sense, i guess, still incase i wanna add an amp if i replace the satellite drivers outright or something, could i be feeding satellite outputs from stock amp of 10w rms as signal input to new amp??... will it be safe for amp board or feasible?