I have used the Tamron 17-50 nonVC.
Bought it to take on holiday earlier this year and sold it (for more-or-less what I paid for it) when I got back... it was cheaper than renting.
Ask yourself this... what is it you don't like about the 18-55.
Unless you really need (and I mean really need) f/2.8 then there is no point in replacing the 18-55.
Yes you can get the Canon 17-55 f/2.8 but the cost compared to the 18-55 does not produce that much difference in IQ.
Most of my shooting is around the 25-30 range, so I just invested in a decent prime instead... I use the EF28 IS USM virtually all the time, and IQ is stunning. It's also quite light weight compared to an f/2.8 zoom.
If I need anything other than 28mm I use the 18-55 IS or 55-250 IS zooms. To be honest they're pretty good.
Lots of folks seem to think that because they're bundled as "kit" lenses they must be rubbish.Strange that if you bought a 5Diii or 6D you'll get a 24-105L lens bundled as a "kit" lens. It might well be an L lens... but technically it's still a "kit" lens.
There are lots of post by folks that think "if I spend more money on a more expensive lens I'll get better pictures".
Most poor shots are simply down to user error and not use of a bad/cheap lens or camera body.
The only reason to change your lens is:
(a) you want more range - wider or tele
(b) you want a faster lens - lower f-stop.