Hmm... well, do you do much low light photography and find you need higher ISO?
Admittedly, I'm kind-of struggling here. If you like your superzoom and find you use its entire range a lot, there is very little that won't require you to switch lenses. There are absolutely better options, but they're either on the lower end of the zoom range or the higher end.
Since you're sticking with crop for sure, we can add EF-S lenses into the mix, which are cheaper than their FF counterparts. If you've ever found yourself wanting more low light capability, plus a little wider for architecture/landscape, theEF-S 17-55 f/2.8 IS USM
is a good option. I'd love to have one of those to replace my 18-55, but have no budget so I live vicariously through others. 
If you've ever wanted to dabble in ultra wide for those landscapes (and architecture), you could look into the EF-S 10-22 f/3.5-4.5 USM
. I'd love to have one of those too for shots like this
or this
. 18mm did ok, but not like 10mm would have.
If you've ever considered shorter primes, I've heard great things about the EF 30mm f/2 IS USM
. Heck, just to play around you may as well pick up a nifty fifty (EF 50mm f/1.8); they'redirt cheap at the canon refurb store right now - only $70.55
. It's my first (and only) fast prime and it's a lot of fun.
There are, of course, better zooms than a superzoom that start a little longer. The one I'd loooove to get my hands on is the EF 70-300 f/4-5.6L
. Plenty of range, L quality and relatively affordable for what it is.
Well, I'll stop there and let someone else make their recommendations too. 