No disrespect intended, but some architects are not very good at designing retrofits. Especially affordable retrofits. If you can find a good one that is affordable, that certainly is the best solution. A good second choice is to find a licensed contractor with good references. Sometimes they have enough experience to do the design themselves, or they have an architect they normally work with for discounted rates. That does put you one step ahead of the game, as you're going to need that contractor anyway. Having one that has a good relationship with the architect will prevent problems that may result from the two you selected not communicating well. The last thing you want is for each to blame the other for any potential problems! Of course, sometimes architects can refer you to good builders, as well.
Just be sure you shop around and get at least 3 bids/estimates. I have a lot of experience with contractors and sub-contractors, I always try to get 5 or 6 bids. Even when getting things done that I don't have any experience with, I've found that talking to that many people who do gives you a very good idea of what is involved in the job and who has the most experience and expertise; it will also give you a amazingly wide range of prices for exactly the same thing.
I just had a small tile entry job bid. Most of the bids were between $500-$600 for labor, but one guy came in and bid $1,500! Had that been the only guy we called... well, lets just say I'd probably have been stuck with doing it myself, as my husband would never pay that much to tile a 5x8' entry (over a concrete slab, no less).
I know its a lot of work to get that many bids. Lots of contractors would be offended to know you did that much price shopping, and admittedly its a lot of work for them to bid your job, but it can save you thousands of dollars and avoids poor quality and many other problems.
And don't forget to check their references, confirm their license is valid (your state contractor's license board probably has a website that you can look them up on as California does), and at the very least make sure they have liability and workers compensation insurance (the latter only if they have employees). I've always required them to provide a binder issued by their insurance company that names me (the owner of the property where the work is performed) as additionally insured. It doesn't cost them anything to do so, its just a hassle for them (they have to call their agent and request it), but will save you a lot of hassle and probably money should anything go wrong.
Good luck!
PS - just noticed you're also in California. Here's the license board link to search by business name:
http://www2.cslb.ca.gov/CSLB_LIBRARY/Name+Request.aspYou can also search by license number. Make sure the business name matches what they give you, and that the person who represents themselves as the contractor is named as such on the license page of the website.