@Sagar93
Never look for what wattage manufacturers give for the AVR with all channels. Only check how much power it would output while driving 2 channels. The power output will drop once you increase the number of speakers attached.
Lets say the AVR is rated at 150watts at 2 channels, it will start to see a dip when you connect more speakers 3 would see 110, 5 speakers would be 70watts and so on.
This also depends on how the manufacturer has built the system, some AVRs like high end models won't see much dips.
Pioneer and Onkyo have a same parent company like Denon and Marantz have. Onkyo is almost out of business, if the Onkyo is available with warranty then try to bargain more and pic it up.
Later you can upgrade to a better receiver.
Sensitivity of speakers will varry between 83-90+ also, higher the number better the utilisation of AVR and speakers. Anything close to 90 is a good speaker. Don't stress on it much.
Subwoofers have its own amplification, much like pre outs. That's why they are called active subwoofers, they power themselves. So don't worry if you have a very high watts subwoofer, higher the better.
@gauravmandawawala much like what
@ktks1 said, go for stereo amplifier or receivers. The sound quality will be very high compared to a AVR. Tons of options to choose from Pioneer, Denon, Yamaha and Marantz. My pick would be Marantz > Yamaha > Denon > Pioneer in this order.
Check out bookshelves or floorstanders, pair with a amplifier and you are done. This is a very simple and easy setup to have good value in sound.