Just wanted to throw something out there and see what sticks. I am new to watches (relatively) and just dig Seikos. I'm not wealthy and don't have a lot of excess income. My most expensive watches are a brass BOLDR Voyager and a little SKX009. I'm interested in affordable vintage and I think ya'll could be a BIG help!
I like the looks of the Boldr's and they run a Seiko motor which makes them even more interesting.
You don't mention if your interested in learning to service your own, but if you are; then don't be afraid to buy almost anything. There are only a few movements where parts have become scares. Things like rotating inner bezels, or date changing mechanisms. Read up before you pull the trigger. If your not planning on servicing yourself than an inexpensive (relatively) watch can end up costing a few more times the cost of the watch to get serviced.
Get into a few "dual quartz" Grand Seiko's (or King Seiko's) from the late 1970's they are still relatively cheep and as the movements were mostly gold plated they last! If you don't like quartz then grab any 21 or higher jewelled watch from 1959 to 1964, they were built during a golden period for Seiko, trying to attract the international market.
Rules are the tools used by fools to sharpen their swords
Vintage watches come in all shapes and sizes. I assume you would like to stay in the around 250 price range for the vintage you would like to buy?
I feel that atm the most undervalued of the vintage timepieces would be dress watches, but I as both of the watches you mention in your post are in the 40 - 42mm range you may not too interested in a watch around 36-37mm .. or maybe smaller.
There was a suggestion of quartz, which is a very good way to go. There are still many 1980's quartz time pieces which are fairly easy to find at good prices.
You may also be lucky and a vintage Seiko 5 for a reasonable price. The problem is the more "funky" the design , the more bucks they bring in.
I did some searching in the last 5 weeks on Ebay and found this.
A vintage (NOS) new-old-stock GALCO 17 Jewel / hand wind "skin diver" from the late 1960's - early 1970's. The case is approx. 38mm (without the crown)and has 20mm lugs. The watch came on the vintage period rubber Tropic Sport strap you see in the image. I don't really like to discuss costs of things, but for this I'll make an exception - under US $300.00 landed in my country.
You could also try Vietnam to late 80's Military issue time pieces. These are vintage and come with a history attached to them.