How big of an upgrade would this be?

Photography is a big hobby of mine, just an amateur / novice but it is something i take seriously

currently, i use a Canon PowerShot SX120

next month i'm looking to get a Nikon d7100

i know it is a significant upgrade (especially the price, 7x lol ) i paid just $200 for my Canon

but i wanted some input and or advice please

The main question is why?
If yo are an amateur/novice, you certainly can't have outgrown the Canon's full capabilites.

It's foolish to upgrade at this stage in your "hobby."

But if you have the money to spend, knock yourself out.
Personally, I'd say go re-read your user manual, and make sure you have used every single custom setting available to you before upgrading to more bells and whistles you will never use…

I would be a huge upgrade.

The Nikon D7100 has a sensor that is over 15 times larger than the SX120.It uses interchangeable lenses and is fully adjustable.

You will be able to shoot in the program mode at first, but eventually you will need to learn how to control the camera using its light meter to get the most out of it.

Here is a link that will help you learn how to balance ISO, shutter speed and lens aperture.

http://camerasim.com/camera-simulator/

You will be able to shoot using selective depth of field, light graffiti, shoot in low light with little or no noise and do many more things with it that is not possible with your nice SX120

Like comparing oranges with watermelons.

Both have manual exposure mode.

The SX120 is a super zoom with one built in lens. The D7100 is a dSLR with an APS size sensor and interchangeable lenses. You will see a big difference in image quality simply because the sensor is much larger. The final outcome will still depend on you. If you couldn't already get good images with the SX120, you will not magically get good ones out of the D7100.

It is quite possible that you have indeed outgrown your bridge camera and are ready for the step up. If you plan to use the D7100 as a P&S on auto, you will gain very little. If you are learning manual mode and are finding the poor high ISO performance limiting, then a new world will open for you when you begin using a dSLR. Plan to spend a lot of time in the user's manual.

Happy shooting!

It's a huge upgrade and not a little investment, but don't be surprised if the images you get from it are not as good as the ones you're getting now.

The camera is capable of far better images, especially in difficult situations such as low light, but to maximise those benefits you have to know how to use it.

The quickest way to learn is to join a club and away you go, in less than a year you'll be glad you upgraded as much more will be possible with your new Nikon, it's capable of techniques you probably don't know exist, but they need to be learnt and mastered. There's a learning curve ahead of you.

If you take it seriously, a good camera is a good idea

It's a huge upgrade, but I don't think you need a d7100 as you're just stepping into DSLR world. I would get the much cheaper D3100 and with the change get an extra telephoto lens and a speedlight to really increase the number of options you have. The D3100 has fewer buttons than the D3100 so you have to dig into the menus more, as well as missing the top lcd. But it's still a great beginner camera capable of taking good pictures and 1080p videos with autofocus. Then, later on, you can upgrade from the D3100 to either a full frame like the D600, or a pro DX.

The D7100 is leaps and bounds ahead of the SX120. The advantages are too numerous to list. The biggest few things that come to mind, that you'll notice right away are:

a.low-light performance. The D7100 will have Way less noise in dark environments
b.depth-of-field. Much easier to blur the background with any DSLR than with a point & shoot, especially with the right lens
c. RAW capability. If you know how to process photos in a program like Lightroom or Bridge+Photoshop, you'll be able to get better colors, sharpness, tones, etc. From a D7100 when shooting in RAW than with the SX120. Then again, you'll probably notice better image quality in general anyway even if you shoot JPEG with the D7100.

Just remember, if you get a Nikon DSLR and lens, you're pretty well tied into the Nikon system from that time forwards unless you want to spend a ton of money switching over to a different brand like Canon.