Just walk away from the Smith machine.
I started this year thinking I was mighty with a squat over 400 and a bench over 300. I ran the madcow 5x5 and everything went up. I was even mightier.
I then got away from the leisure center I was working out in with its one and only Smith machine and went to a hard core gym. At first I had trouble benching 135 due to atrophy of the stabiliser muscles. The bar was all over the place. After a couple of weeks I had a very wobbly 250. It's taken four months to get almost back to where I was.
The squat was the same. My knees didn't have the support muscles and neither did my thighs and hips. The Smith does too much of the overall work for you and I went from thinking I was almost a 450 squatter to realising that I was barely a 300 squatter. I'm nowhere near back where I thought I was with squat but I can feel the improvement almost any time I have to push aganst the floor.
The good side? My chest and legs are fuller from the free movements. My stabilizing muscles now are able to do their job in helping with the lift and if I have to do the movement in the real world I know that I'll be able to do it without having a whole bundle of untrained support muscle pop under the load.
The bottom line is that the Smith is a very restrictive machine and to train on the Smith without, at least, also working with free weights will leave you with a lot of muscle imbalances that you won't even suspect you have. Your real-world strength will be just a fraction of your gym strength and correspondingly you're an injury waiting to happen. The tragic thing is that I didn't have a clue about my weaknesses until I went to free weights.
Free weights work you much more and force your body to provide its own support and stability. You can get stronger on the Smith machine but you'll do it faster and in a safer and more complete fashion off and away from it.
I've never tried the angled Smith.