I'd just like to mention how nice it is to see someone so interested in glass...and realizing the importance on the final outcome...
Instead of worrying constantly about a new body
Great choice...upgrade your glass. Some excellent suggestions so far, but I would say, to take the next step up in quality; both build and image...the choices would be for a wide set up:
The Canon 10-22, Sigma 10-20 or Tokina 11-16
for your standard zoom
The Canon 17-55is (really hard to beat at this price, on a crop, an even better choice, IMO, then the 24-70L, ymmv). This is a HUGE step up in quality and digs a lot deeper into the wide angle than your curren 28-135.
for your tele
Check out both Canons....the 70-200f/4 versions with/without IS. You can pick it up for just over 600 bucks without IS. Excellent lens, L build and image quality...a VERY sharp zoom, indeed.
Or you can pick up a set of primes. Find the FL(s) you enjoy shooting with your current lenses and pick a couple of primes. On a crop, there are a ton of good choices....including excellent third party options from Sigma (the 30 and 50mm 1.4s) Canon has a couple of 50mm options, and 85 as well.
Lots of great choices...but the 17-55is and 70-200/4is would be the first two I would invest in, in your shoes
That's essentially take you from 25mm to 320mm....with excellent image and build quality (these two lenses will last you a couple decades, with care)
Then, grab a Sigma 10-20 and you're good to go!
I know, I know...first you gotta come up with 2 and a half large...but that's all there is to it
Good Luck