I dont find there is much difference in 20.1 and 22, but when it comes to load on GC .. 22" with full resolution is quite high.
Get a better quality (type of panel,response time,viewing angle) 20.1 than a 22
And you GC can support 22" happily. At last .. LCD price and specs are really going fast, if you wait until DEC .. i am sure you will get better deal.