Modulating furnace with single stage AC -- good or bad idea? (X-post)

Hi,

This is a x-post from /r/hvacadvice

So we're currently in the process of getting bids to replace two 28 year old Lennox Pulse systems w/HS18-311 outdoor units. We've had two Lennox dealers come out to provide quotes, but I'm confused by the conflicting advice. For reference, I'm located in Central WA, adn the EPA estimates 500 full-load cooling hours for our area. Our house is 4300 sqft, single level running east-west. Bedrooms are on the west, family/kitchen/office (work from home) are on the east.

The first dealer (did load calc) said that for our area, he wouldn't go anything above an XC14 AC unit with either SLP98V or EL296DV furnaces. Says the price jump to XC25 or SL18XC1 is too much and we'd never "break even". The second dealer quoted same furnaces with either XC25 or SL18XC1, and said if you get modulating or two-stage furnace, you should get AC unit to match or else you're loosing the benefit of the multi-stages for half the year.

Who's right here? Prices for these options ran from $11k-$15k depending on options and combos. I've decided that our utility bills are already low enough that we'll never break even on anything we do, but it's very important to us to stay cool in the summer and we'd like to reduce the amount of dust in the house (add extra filtration to whatever we decide).

Also, the load-calc says the unit on the east side is slightly undersized, so we'd be bumping from 2.5T to 3T on at least one side of the house.

Any thoughts?

Thanks

submitted by /u/branfarms
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