Josh, are you confused enough now? I've been studying mics for 2 1/2 years, and I got confused reading the posts above. Let me try to sort it out a little.
First, you could hardly pick a more useless pair of mics than a C3000B and a C1000S. The one thing almost everyone (including me) will agree on is that with $400 in your pocket, you can do a hell of a lot better.
Secondly, "stereo" recording is not just using 2 mics and panning them left and right. Stero recording is a scheme, with several different versions, to use a pair of matched, or at least very similar mics, to simulate the picture your 2 ears would hear if you were in the actual room listening to the music. You can make lovely recordings of an acoustic using 2 (or more) very different mics, but that is *not* stereo recording, that's just recording with 2 mics, which, as I said, is also just fine. It doesn't have to sound just like it sounded in the room, if it sounds *good*.
Third, the cause of the many answers you get is that the needs of acoustic guitar recording and vocals are somewhat different, so either you use different mics selected for those 2 different purposes, or you choose a compromise between the 2. Both plans can work. Often, when 2 different mics are used to record acoustic, one small diaphragm and one large diaphragm mic are used. Most vocalists will do better with a large diaphragm mic, and most people like one or two small diaphragm mics for acoustic. As a rule, I'd rather record an acoustic with a large diaphragm mic than a singer with a small diaphragm mic. However, there is a class of small diaphragm mics with larger housings that *look* like large diaphragm mics, which are among the best compromise mics I mentioned above. So-
Now we have enough info to consider some $400 alternatives from the selections above. The first suggestion was a MXL V67G (LD) and a pair of MXL603's (SD). That's not a bad suggestion. That gives you a stereo pair, and the option to use one of each on the guitar. Go ahead- try singing into a 603, and you'll find out why most vocalists don't use SD's. The V67 would be OK for that, though.
The last suggestion was a pair of C-4's. They are a very good stereo pair of SD's for the price- Good for guitar. Using them for vocal mics is not a pretty thing. The only vocal mic I can think of that could then be fit into the budget is a Studio Projects B-1, about $80. It's not one of my personal favorites, but it works for some people. Somebody will chime in and suggest a dynamic for vocals, and that can work if you have a good preamp and the right voice. But I was trying not to confuse you.
I should mention a couple of "workhorse" mics that are compromises. These are small diaphragm mics in larger housings that you *can* use for vocal mics or for guitar, and which can be used as a stereo pair also. My favorites- AKG C2000B and Audio-Technica AT4033. The 4033 is pricey, and one would take most of your budget. The C2000B can be had for $180 with the shock mount.
A side note here- the Oktava MC012/MK012 was mentioned above. This is a Russian made SD which is a pretty good mic, but they are becoming increasingly difficult to get, and service or replacement is currently nonexistent. I like them a lot, but I wouldn't choose them in your situation.
Hopefully your knowledge base has been increased enough that I can now give you my suggestions, and they will make sense.
Iwould chose a pair of MXL603's ($154.95 at 8th street) and I would pick up
a C2000B with the shock mount ($179 at 8th street) or the V67G ($99.95 at 8th street). If you bought the V67G and the C2000B on ebay, it would drop the C2000B to $150 or even less, and the V67G to about $85, bringing in all 4 mics for under your $400 limit, and gratly expanding your options for recording voice and acoustic. Hope this helps. Good luck-Richie