On front options, I just completed a 'no front bar, higher spring rate' alternative that seems - I don't know, pretty good to me. Suspensions are pretty complicated so I don't want to go too far in saying 'this works'. So let me just describe what I got and how it seems.
First, I took out the front bar and ran stock springs for a day. Note that I have cut 1st gen Miata rear springs in the rear, about 9 1/2 inch free length, 150 lbs/in (there's pics and stuff somewhere above). As I mentioned earlier, 1 out of say 3 or 4 layers of noise disappeared. It was a bit quieter. I took the car to a wet parking lot and tried to push it through 90 degree corners. There was a lot of body roll, but the balance felt pretty even. I wasn't getting the front end to push (under steer) or the rear to swing out (over steer) - on wet pavement...
I wanted to try a higher spring rate at the front to see if it'd help the body roll. Long story short, I ended up buying a set of 'lowering' springs for a 2006-2009 Honda Civic. The fronts were listed as 230 lbs/in, the rears were listed as 140 lbs/in. Total gamble - I just figured they looked like they might work, and if they lowered the 2006-2009 Civic (the ad said 2 inches), they might keep the Insight roughly the same. etc etc.
The rears didn't fit - the bottom coil was just a tad too big, but I wasn't planning on using them anyway. The fronts - I needed to order an extra right side spring; the civic has left and right hand springs, whereas the Insight front springs are the same left and right...
I measured the fronts and calculated the average spring rate as 204 lbs/in - but they're a progressive design. I'm not an expert, but the way the springs work is that the 3 middle coils have a larger diameter and they compress first; the top and bottom coils are smaller and do most of the heavy lifting. I calculated the spring rate for the middle 4 coils as being 170 lbs/in, whereas the top and bottom coils combined come out to 510 lbs/in... There's very little travel at the 170 lbs/in rate; the middle coils are almost fully compressed with the car's weight on each corner. There seems to be enough 'middle coil' travel to absorb your average bump nicely; and then, when you push it through a corner, the higher rate portions of the springs seem to hold up each corner well...
I've only driven once with this setup and didn't really push the limits. Overall I'd say it rides nicer than stock now; without the bar, each wheel absorbs single wheel bumps easily. I have little fear, now, of hitting bumps -- I used to try to avoid them but on this inaugural trip I was hitting all the bumps I could find and none of it felt violent, at the least...
Ride height in front dropped about 1/4 inch - which is good for me because my cut Miata rears dropped the rear about 1/2 an inch as I recall (it was either a 1/4 or 1/2)...
Anyway, moral of the story at this point is simply that, if you're looking for alternative front springs, you might consider looking into two
right side 2006-2009 Civic lowering springs. They fit almost as well as the stock springs. The middle coils are a bit bigger than stock, yet I don't see any clearance issues, and the 'top' isn't quite as flat as the stock; they're not ground down, for instance... I bought my set for the grand total of $70 - from an ebay seller called Ipex motoring. I didn't explain that I was trying to fit them to the Insight - after I discovered that I needed another right spring. I just said I needed another right spring and after a couple emails back and forth they sent it to me (I did offer to pay extra and did offer to send the left one back, though). I was afraid of getting stuck with 4 useless springs and $70 poorer, otherwise I would have been more up front. If something like stronger front springs, progressive, with 1/4 inch of lowering, sounds like it might be right for you, you might want to try Ipex and ask them to sell you 2 right front springs. But alternatively, there's a bunch of different options - like Tein, for instance, who make similar springs. They're more expensive, though. These 'Ipex' springs are probably bottom of the barrel...
Oh, btw, the front bar is really light, whereas these alternative springs are quite a bit heavier than stock. I didn't weigh anything, but I'd say it's probably about a wash - lose the bar, lose some weight, get heavier springs, gain that weight back...
Here's a couple pics, I'll have to take a couple more with them installed: