What direction if any should a long wire antenna go and is a Beverage Antenna something I can try?
A longer wire might be worth trying, if you have the area to put it up.
When you get a wire antenna that is more than a wavelength long (somewhere just above 100 ft. for the 31 meter band) the antenna starts to get directional off the end of the antenna (sort of like a cloverleaf).
So if you live in a valley (you haven't said how narrow the valley is, or how high the hills are), run the long antenna diagonally, with the end pointed diagonally towards either end of the valley. I had a 100 ft. antenna set up diagonally in the valley where I live (approx. 150 ft.hills on each side, which degrade reception from those directions) and it worked very well.
Depending on your signal strengths off the antenna, a longer wire may overload your radios. It's possible the World Receiver and DX-100 would overload (I don't know anything about the Grundig), but you would get more signal with a longer wire. You'd just have to deal with overload images. You may get RTTY sounding interference in the middle of a shortwave broadcast band on a couple frequencies. If you tune the utility frequencies between SW bands you may hear images of SW stations there.
I was able to run a 100 ft. wire into my Realistic DX-390 in the 1990's (before the antenna blew down) and had relatively little overload -- about the same as I get on my 25 ft. indoor wire. But then, I don't live in a high signal area. My RS PLL World Receiver 20-629 has roughly similar circuitry inside (4 stages of IF filtering on SW, 3 IF amps), so I'm sure at my own low signal location it could probably handle 100 ft. o.k. as well. But it would also get images. It works the same as my DX-390 off my indoor wire (a handful of images, mostly in between SW bands), so I'm guessing on a longer wire it would be the same.
At other locations in the U.S. a longer wire could overload the radio a lot worse. Even a 15 ft. indoor wire on my DX-390 made my radio virtually useless when I took it with me to northern Louisiana (it worked great off the whip, though). So keep this in mind. When you have radios that aren't $500-1000 tabletops, there always is a tradeoff when you use a longer antenna (overload vs. more limited reception) -- you just have to work within the limitations of the radios.
If your radio overloads you can always switch in the attenuator switch (DX/Local switch on the left side of the World Receiver) to "Local". If your DX-100 or Grundig have RF Gain controls you could crank them down. Another trick using a portable with a longer antenna is using the whip antenna on the radio, and placing it near the end of the long wire without actually touching it to the wire. You can still get some enhanced reception, but the radio won't overload as much.
I don't know about your other radios, but the World Receiver has internal diode protection on the external antenna jack only. So if you attach an outdoor antenna to that radio use the external jack only. If you attach it to the whip antenna you will risk zapping the RF amp FET transistor if there is a static discharge.
If you use a long wire it might be a good thing to build that antenna protector frequently posted on this forum (a simple circuit using diodes -- another poster here has the schematic) to keep static from zapping your radios. A little extra precaution never hurts. Even just two diodes between the antenna and a ground (in reverse polarity from each other) will bleed off static electricity.
It still would be helpful if you could tell us more what you are hearing now -- how many stations -- even if you don't understand the languages of the stations.
Hope this helps some.