Well Pete my first beef with your shirt choices is that they are of the cheaper variety. I'm 5'8" with a 44" chest and about 200lbs as well. Nice to still have a 34" waist so I understand about shirt fitment.
Are you wearing a tie or doing the business casual?
If your wearing a tie I suspect your neck is abnormally large, so you may want to head to the Men's Warehouse and ask their staff for some collar extenders. I advocate buying NOTHING in that store as they sell crap. but getting a few collar extenders will give you an extra 1/2" and you might be able to get by with a 16" 34-35 off the rack shirt or at least a 16.5" collar. 17" and your really getting the balloon look I bet. A double windsor will give you a broader knot so that your shirt collar doe not look spread as well. Another tip is to remove the collar button and resew it closer to the edge.
For brands, try Hart Schafner Marx, Polo, Tommy, Joseph Abboud, Ike Behar, Facconnable, & Nicole Miller. Stick to 100% cotton as well.
