Advice on prime lenses for Canon crop sensor
I am looking to purchase 2 more primes to add to my 600D and Sigma 30mm. Most of my 5D full frame buddies go with 28mm, 50mm & 85mm on theirs. What focal lengths would you recommend to complement the Sigma's 30mm. and Canon crop sensor? Personally I'm thinking a wider and a longer lens (24??, 85??). I am DEFINITELY NOT looking to purchase a zoom as I like primes for their depth of field and forcing me to move to frame a picture. I don't have the budget for L glass and find it difficult, especially with wider lenses to find something decent yet affordable. I could probably stretch to £400 each lens. So far from my research Sigma seem to outperform Canon's wider non L lenses so one of those could be an option (I am well aware of Sigma's 2-3 week calibration turnaround thanks to my 30mm!).
On the photography side, I like landscape and arty architecture shots. Not so keen on portraits although I get coerced into the family photo stuff, esp with a niece/nephew on the way any time soon!
Please feel free to share with me your personal opinions!