Frankly, since your budget is 10-20k you will get better sound if you customise a set (like what ronnt88 suggested). If you go to places like Best Denki, Harvey Norman, etc they will have some sets from the mass market Japanese brands like Pioneer, Sony, Yamaha, Onkyo, Denon, etc... it is more convenient but overall you will get more of your money's worth by customising a set by going to the hi-fi shops.

There are so many brands out there... PSB, Klipsch, Wharfedale, Mordaunt Short, KEF, etc.

Please visit some shops to listen to them and see what you like. It does take some effort to visit different shops to listen to different stuff. Also means it might take some time before your whole system is assembled.

Try to visit shops which have a large selection of brands. So more choices for you to mix and match and if you buy a system from them can nego for better price.

Marantz is another good choice for electronics, like CD players, AVR, etc. Audition them and decide for yourself.

I think by "standalone AMP" you mean the AVR. Usually the AVR will have a higher quality amp and higher power. AVR might also have more HDMI inputs, might have upscaler and also room correction feature like Audyssey. You can check the features between an AVR and HTIB and compare.