Best Stero Receivers Need Help Matching My Receiver With Speakers. Watts? Ohms?

Need help matching my receiver with speakers. Watts? Ohms? - best stero receivers

I recently bought a 5.1-Samsung HT-7200DH home theater. I know I should just buy the receiver and speakers separately, but it is too late. I have the following information from the manual:

TOTAL ENERGY AND THD:
With 6 ohm loads, both channels of 120 - 20,000 Hz, nominal 90 watts per channel RMS power, with no more than 1% total harmonic distortion of 250 mW.

AMPLIFIER SECTION
Output power (at 120 V AC, 60 Hz measured)
Stero mode (nominal)
(6 ohms, 1kHz, 1% THD)
90 W + 90 W
Surround mode (reference)
(6 ohms at 1 kHz, THD 10%)
RMS output
FRONT: 140 W per channel
CENTER: 140 W
Surround: 140 watts per channel

I get really 140W 5-Channel?
If you have purchased, 200 W, speaker of 8 ohms to the speakers that include wimpy would replace it a problem?

This is an 8-ohm receivers than 6 ohms?

What is the total harmonic distortion?

I will not buy big speakers, this receiver is gOOD.