Replying to New skis

Here is my situation: I am 135 lbs 5'7 on junior Rossignol S7.pro skies which are 160cm in length. I skied 38 days total last year at Alta and once at Brighton and Snowbird. I greatly improved from the beginning to the end of the season. Right now I am a pretty good skier I would say. I always have room for improvement but I feel pretty good about my skiing, I can do some cliffs and 360 and that but this year I want to make a significant improvement, and I would like a ski that can do switch powder landings if that means mounting the bindings forward slightely. Last time I used my skis was about 8 months ago and I grew an inch or two since then. A problem with my skiing last year was I didn't feel very stable going fast on the choppy stuff like on those run-outs that you kind of have to straight-line were kind of rough. Also on the deep powder days I had to lean back a considerable amount to keep my ski tips up other wise they tended to dive in unless I kept a pretty good speed.

So I am wondering now, where I start. If I got new skis it would probably be for Christmas and I would have a budget no doubt. I have $180 now and I was thinking I could sell some things to get to $230. If I got new skis, my current ones would have to go. I couldn't find anyone selling my skis used on ebay so I don't know what to value them at, they are decent condition with some top surface scratches and they just got base grind, edges sharpened and waxed. They have Rossi bindings that I think MSRP 159.00 and have a 100mm brake and have 4-12 DIN. Right now I am not even sure about what route to take for selling them, whether or not to sell them with bindings mounted or sell them taking off the bindings and get the holes plugged and then carry my bindings over to new skis. I planned on getting skis at least 105mm waist so I would either have to bend the brake or get a new brake. Which would be the most economic option?

I don't know exactly my budget but it would probably be how much I get for my skis + $180(maybe 230) + maybe $200(as a last resort I would sell my Mtn. biking neck brace which I don't know about just yet). I would like not to get a ski over 600$ though. I could get the bindings for Christmas so long as they are under 250$. So, what do you reccomend if I go the used route of buying skis pre-mounted like this: http://www.ebay.com/itm/2010-Salomon-Czar-Rocker-Shape-Twin-Tip-Skis-166cm-w-Salomon-Z12-Ti-bindings-/150692881728?pt=Skiing&hash=item2315fee540 the only bummer is I couldn't have say as to where the bindings are mounted (correct?). Or getting new boards off of Ebay: http://www.ebay.com/itm/Surface-One-Life-Skis-179-/130593514341?pt=Skiing&hash=item1e67fae365 I would like a ski that's rockered and at least 105mm underfoot like a Czar. I don't care a whole lot about how the ski performs on groomers oh and I don't ski park.

So yeah, sorry it's pretty long but I feel like I could just ask endless questions, but if someone could fill me in on all of my questions that would be golden

Thanks