sjsoggy,
Unfortunately … post #2 here which is centered around Portland includes the manufacturers that I know of that are closest to you. Outlets in Newberg and Beaverton are the closest but they are also very close to Portland and not so close to Eugene.
Some of the other manufacturers outside of the Portland area (All of which are further than Portland) that are in or near Oregon (as a reference for others who read this thread) include …
http://www.kramernaturalmattress.com/ Factory direct manufacturer in Sprague River. Sister site to Mulligan mattress in Portland. They both make a simple high quality latex 6" + 2" latex mattress and a solid wood bedframe that has good quality and value.
http://www.mattressfactorynw.com/ Factory direct manufacturer in Bend, OR and Moxee, WA. Local factory direct manufacturer that makes a range of latex/innerspring hybrids, gel memory foam, and high quality traditional polyfoam mattresses that use 1.8 lb foam and higher. they are also planning to build a Dunlop all latex layered mattress. They also carry Pure Latex bliss. Some good quality and value here.
http://qualitymattressgp.com/home/3550124 Local manufacturer that has been making mattresses in Grants Pass for 35 years. They make latex along with one and two sided spring mattresses and also carry Englander and Northwest Bedding as well. Will also custom manufacture and rebuild mattresses and are transparent about the materials they use in their mattresses. Well worth a trip for those that are in reasonable driving distance.
Mattresses & Toppers Archives - Shepherd's Dream Manufacturer with locations in Ashland, Montague, and Mt Shasta that makes an all wool mattress.
http://www.kellygreenorganic.com/. Manufacturer in Shady Cove, OR. They also make an all wool mattress using Ecowool for those who are looking for this style of mattress.
Furniture Row® Store Locations - Store Hours & Addresses Salem, Central Point, OR., Kennewick, WA., Boise, ID. Regional factory direct manufacturer that makes a wide range of mattresses including a latex/polyfoam hybrid that can be purchased with a latex or memory foam topper and traditional innersprings using higher quality foams. I would avoid the mainstream brands they also carry. Some good quality and value.
There is also a Wholesale manufacturer in Portland called http://www.easyrestinc.com/ who makes some high quality and value memory foam and gel memory foam mattresses with good value and they have a list of retailers on their site so you can check which are closest to you.
Locally there are also a couple of local retailers that carry a number of alternative brands that may have better value although you may need to ask good questions about the materials in their mattresses and/or make some good value comparisons. I would avoid any major brands they also carry.
http://www.ecosleepsolutions.com/ Retailer in Eugene that carries Savvy Rest which is a component latex mattress that can be customized in many ways. They also carry Royal-Pedic and Savvy Rest innerspring mattresses as well. These are all high quality mattresses but are also in a more premium price range so make sure you make some careful value comparisons.
Robb's Pillow Furniture, Futons, Beds & Bunks - The Better Bean Bag Alternative Retailer in Eugene that carries Easy Rest and Cotton Cloud (including latex).
http://maniadeals.com/matty/ Retailer in Eugene, Springfield, Corvallis, and Albany that carries Restonic, Easy Rest, and Sound Sleep mattresses.
http://www.mattresscompanyeugene.com/ Retailer in Eugene that carries Englander latex mattresses.
http://www.bedmartmattresssuperstores.com/ Retailer in many areas of OR. Easy Rest and mattresses from Northwest Bedding which may have some better than average quality/value.
http://www.americanmattressstores.com/ Eugene/Springfield, OR. Easy Rest.
http://www.brennersfurniture.com/ Eugene, OR. Lady Americana.
Your option of using a durable coil mattress and adding a topper can be a good one but it’s not so easy to find a good value “durable coil” mattress with a firm innerspring that doesn’t have too much lower density polyfoam on top to make your plan worthwhile. If you buy a lower cost mattress that has too much low quality polyfoam that softens … then a topper will just follow the soft spots in the mattress. If you do buy from a local manufacturer then they will usually change out a layer for a reasonable cost which is similar to buying a new topper and there are also manufacturers who sell zip cover options with independent layers inside where the layers can be changed as well that also have very good value.
If you find a suitable base mattress though with only minimal amounts of polyfoam with good value … then this can be a good way to go.
Hope that helps … and I would consider a trip to the Portland area. It may be some driving time but in the end it may save lots of frustration and research that can sometimes feel like pulling teeth 
Phoenix