I don't like anything posted by that guy (stuckincustoms can'tbearsedtorememberhisname) and so won't be using him for a (drunken) comparative point.
What I can say is that if you feel you need low-light performance and are willing to suck up the potential expenses associated with getting a DSLR, and have specifically been taking photos 'for years', then a used 5D Mk I might be worth looking into. I can't list a Nikon equivalent purely because I don't know which would be appropriate to talk about, but look into them as well if you're better informed than me.
So to move on - as a rule of thumb no matter what you get - compact, superzoom bridge, entry level or 'pro level' SLR, you're going to get an improvement on low-light performance. You're going to get an improvement on resolution. If you go the Canon route you're more likely to gain RAW format by way of
CHDK than not (it's potentially available for your camera, I'm too drunk to look into it accurately).
What you won't, obviously, immediately get from going for a new compact or superzoom is as high a *potential* quality as with a DSLR. Specifically, you won't necessarily gain the functional advances that most DSLRs offer. DSLRs are, in my opinion, largely about getting the larger sensor size for the greater björkeh OR gaining in the functional advances that the controls of the camera themselves lend to your operation of the device. In particular, with most compacts and superzooms your focus is based on contrast detection performed by the computing power of the camera 'in-body' as opposed to a dedicated autofocus mechanism that scans for horizontal and/or vertical line coincidence - completely independently from the exposure metering as well as overall 'scene detection' mechanisms present in your camera.
These obviously affect the camera's ability to 'automatically get things right' for you with minimal intervention on your part. In that sense, having more AF points (read: Canon 7D or Nikon Dwhatever) could be important for a real, tangible difference. Simultaneously, lenses with decent AF mechanisms would also be important.
So what you need to think about and take into consideration at this point is whether you genuinely need something the likes of a DSLR versus a Canon G12 as a pinnacle of (canon line) fixed-lens semi-pocketable cameras, or if you're willing to deal with the bulk and general inconvenience of a DSLR.
As someone that has used a DSLR for over two years now versus a compact camera for around half a year, I can tell you now that I frequently miss the overall convenience of a pocketable camera for general 'photography'. Yes, a DSLR can potentially provide greater-quality photos with a narrower depth of field when I want it, but it's not something I can take with me to nearly as many places as I'd like while still having the breadth of control I desire.
So if what you want is a higher-performing camera, you need to take into consideration just what degree of low-light you want to work with, what degree of wideness in and telephoto-length of focal length it is you want to work with, and just how much björkeh it is you desire. The G12 has a big sensor for a camera of its type - almost Canon 1.6x APS-C format - and with its f/2.8 constant aperture lens can so provide ------ aaaand I dunno what I was doing here - I just spent the past hour and a half typing up a semi-breakup-message to a female in the middle of typing this, and am now substantially drunk.
