Nice dress shirts.

I'm looking for some dress shirts that I can wear with a cardigan or just by themselves. I have a blue cardigan like this one and a gray one like this.

My question is: What kind of pants should I wear with them while wearing the shirts by themselves and with the cardigans and I was wondering if anyone could give me colors that you think would work with these cardigans and if you could possibly advice me on where to look for these shirts.

Thanks MFA.