I agree with a lot of the other responses.... you don't really need a new camera and you've got some good lenses too.
You need to learn to "see". The biggest thing with all your image examples is that they look like snapshots... taken quickly without any planning or much forethought.
For example, if that mission is near you, go back and spend some hours.... maybe even a full day... just wandering around it and looking for things that catch your eye, then figure out how to capture them in the best possible way with your camera. Take what you've got... and maybe not even all of it... and DON'T buy more gear. That will just make matters worse. You can get "lost" in too much gear, never really getting the best out of it.
Also learn some post-processing techniques. There are many things that can be done, too much all at once... but can be learned over time. I've been using Photoshop since the mid-1990s, but am still learning new tricks with it. For most people I'd recommend something simpler and with more guided modes, such as Adobe Elements (it has Beginner, Intermediate and Expert modes).
You picked a very difficult subject photographing a black cat! (I know this because I have your cat's twin sitting here glaring at me with much the same expression, wanting her dinner
right now.)
This portrait of a friend's cat was photographed some years ago with a much less capable camera than yours.... a 6MP Canon 10D:
Notice the background in the above image. I shot by window light alone, so it went very dark, but I still had to retouch out a little detail that showed up. I did little other than that to the image. It was shot with a standard 50mm lens, which works very well for portraits on crop cameras like ours... acting as a short telephoto. I used a fairly large f/2.8 aperture to blur down the background as much as possible... But also not "wide open" so that there was enough depth of field to capture the whole cat reasonably sharply focused, but also because I know from experience that lens isn't particularly sharp wide open at f/1.4 and that it sharpens up very nicely when slightly stopped down.
Looking at your cat photo, the first thing I noticed was that there's some slight greenish "eyeshine"... the reflection of the flash from the cat's eyes. That photo is very sharp and has lots of fine detail! But the flash is a little too strong, too... Causing the image to be slightly over-exposed. That's because all metering systems try to render things "middle tonality". A black subject will tend to be overexposed. A white cat would tend to be underexposed. Your camera and mine have Exposure Compensation that allows us to adjust for this. It's something you can learn to use, over time. The first thing to do is simply start noticing when things you're photographing are unusual tonality... not "average", but darker or lighter than usual. Flash also tends to look a little cool.
I hope you don't mind, I took your cat photo into Photoshop to fix the redeye (using a color replacement tool and burning in the blackness a little). I also dialed back exposure slightly overall, but put a mask in it so that I could "bring back" the detail in the cats fur. Finally I boosted color saturation a little, which brightened the cat's eyes and slightly warmed the overall image (if it hadn't warmed it, I could have added a warming filter). See what you think: