The EF 28-135mm was designed for FF and not optimized for APS-c sized so it's actually softer than the 18-55mm's range and as stated before 28mm is not very wide. At the long end compared to the compared to the 55-250mm the 28-135mm is more or less the same giving or taking depending on what focal length.
The EF-s 18-135mm is even worst, just more range not any sharper. On the long end however the it is about the same as the 55-250mm and actually sharper at 135mm noticebly.
I would not recomend any of these lenses above and would recomend the 17-55mm f/2.8 IS (the sharpest lens for 1.6 bodies), 15-85mm and Tamron 17-50mm f/2.8 (cheap and sharp). The Tokina 11-16mm woud be a great addition to the kit as well.
If you could stretch for it a used 5D II or 6D would give much bigger IQ jump with the 24-105mm f/4 IS or even better with the 24-70mm f/2.8. To compare with the ISO 112233 charts, start with the same equivalent focal length for both bodies (24mm for FF and 15mm for APS-C or close to it), and the same DOF (about 1 1/3 stop but one stop is close enough if thats all the is given), f/3.5 for APS-c and f/5.6 for FF. That way you get the same image for both formats, don't worry about noise because there is a 1 1/3 stop advantage of noise for FF (5D II probably a little more for the 6D) so use a higher ISO to match the exposure. You will find that FF has a very nice IQ advantage compared even to the best lens for APS-c.
But if you need or want speed then that disqualifies it.
Hope this helps,
John.
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