Need some advice

I'm in MN. I got a quote from a local company to replace 17 double pane low-e vinyl windows and two patio sliders (crappy cookie-cutter builder grade from 1994). We have a lot of air infiltration from all directions in this house. We have a drafty house in the winter and a horribly hot house in the summer (front of house faces West and gets really hot in the evening).

Most of our sliders are 58" x 58". The quote was for $20,500 for Heartland Ultra Dual Cardinal 366 two lite sliders mostly and a few double hungs. U-Factors are 0.3 and SHGC is 0.2. My parents installed these windows last year and they look and perform really well from what I can see.

My budget is $20K, but I was hoping to spend a bit less than that on windows and be able to get a new HVAC system (ours is 18 years old) and more insulation and air sealing. I'm a bit disappointed that we might not be able to accomplish all that with $20K.

We already have low-e double pane vinyl windows. Every winter we 3M plasticise all of them and it is a PITA. I wonder if we will really see any improvement by getting new windows? Are they going to be the same? The windows seem to be better constructed, but that is an aweful lot of money.

I'm waiting on sales people to come for Marvin Integrity fiberglass and Serious fiberglass windows as well. We plan on staying in this house pretty much forever.

Thanks in advance for your thoughts.

Both of the other two companies that you have coming are going to be high priced.
Your budget is more than enough to get great windows and doors. The quote you have is not for a great performing window, you also need to have the AI (air infiltration number) to properly evaluate the products.
What part of MN?

Its impossible to say how much improvement that you'll see based on several factors including the condition of your existing windows. What I can say, is that the 366 glass package is not ideal for your area (shgc too low), and then I'd echo anthony's sentiments. Those two windows are going to be pricey, likely not offering the best value (although the Marvin is very nice). I'd check out some other, higher end vinyl products. Sunrise, Gorell, and Softlite should be available in your area, and I know that Richlen and Gerkin are decent, popular choices there as well.

Get and energy audit and get some real data on the home.

With 17 windows, you should be able to get a really good window and get the home air sealed and insulated in many cases.

Do you research and your home and utility bills will love you for it.

+1. Good advice ..... I'd say builder grade vinyl from 1994 is likely at its life expectancy regardless, but an audit will help identify all the areas of concern and prioritize accordingly. Many states have programs where you can get them free, discounted, or at least get rebates on the work once its been completed.