Is a 20 Karat diamond too much?

I'm not sure that there is really anyone outside of the British royal family that has diamonds that big. I'm sure that you meant a different size. If you are not limited on budget, the bigger is usually the better but it really depends on the person. I think you better talk to your partner and see what she feels.

it is definately very big.

More Karats, more Expensive.

It depends on person to person that how much they wanna spend on diamonds.  Quality of diamonds depends on many factors like colour, shape, cutting and all..

Its definitely not too much, but apart from the royals in ancient times i suppose no one else would like to wear such huge diamonds. Today, jewelry with small diamonds are considered much trendy.

Yes!

I myself bought my girl firend a 20k, Diamond ring. it cost £5,500, which is $11,000. Granted, i had won the equivaland of $540,000 on football(soccer) betting, two weeks previous.

   if you do get a 20K ring, its best to get it wih loads of smaller cuts, rather than one single huge diamond, as i did. one huge diamond, while impressive, can be heavy. loads of smaller cuts of it, look much nicer, and are more convinient, while still remaining rare and expensive.