Hi. I'll try to keep this short and not turn it into a rant about how there are no good guitar shops near me, but I apologize if it starts to turn into one.

I live in Austria, which is by no means the best country for shopping. There are many guitars I've looked at online in the past and never been able to try simply because they are not in stock in any of the guitar shops here. I'm on a trip to England soon and I may get a chance to visit a large guitar shop (Hank's guitars in London) supposedly they have over 1000 acoustics. Recently I've been having a look at buying a nice acoustic (6 string, with electronics, up to 1,500 pounds) and I'd like to take this opportunity to play as large a number of guitars as possible, I want to try all the guitars I've read about on here but have never had a chance to look at: Alvarez, Martins, Taylors, Takamines, Cole Clarks, Breedloves, Seagulls, etc. I'd just like to hear of any suggestions from you guys that are worth a play if I get the opportunity. I don't even mind if they're not in my price range for a potential buy, I'd just like to try as many guitars as possible given the opportunity so that in the future when I do end up buying a nice guitar I have had more of an experience with top end guitars and have something to compare to. That being said if I do find one guitar that I absolutely love I may just take it home.

tl; dr any recommendations for guitars that I really should try but have never had the opportunity due to a lack of stock in my local guitar shops.

Couple to add to your list:

Simon & Patrick
404: Sig not found.
Maybe I'll go with you, just for fun. I haven't been to Hank's yet. Just joking. (No I'm not)
Basically, the brands you mentioned and every other guitar you can find.
will someone carry me across ten thousand miles under the silence
Epiphone Masterbilt and Guild GAD series. Both are very well built. The GAD 50's are quite the lookers too.
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- Martin D-16RGT w/ LR Baggs M1 Active Soundhole Pickup
- Seagull 25th Anniversary Flame Maple w/ LR Baggs Micro EQ

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Get the sales guy to play the intruments you may be considering, and if possible to do it in a way that you are blind. Turn your back to the sales guy as he plays the instruments and see what you choose based on the sound that appeals to you best.
Martin, Taylor, Larravee, Alvarez, Yairi, Cole Clark, Tanglewood...... and the list goes on. There are more guitar companies than any one person can know or have played all possible selections from, so really, you have to trust your ear. There are a lot of smaller almost unknown luthiers out there that make great sounding instruments in small out of the way shops, so don't count anything out until you ask lots of questions. 1500 pounds is going to get you one heck of a nice sounding guitar no matter the maker.

Also think about the sytle of guitar and music you like to play.... . does it like booming bass or bright trebles, or do you vary your playing an want something that has a decent balance of both. Even your physique can come into play. I'm a big guy, and even a dreadnaught is a little small for me... and so a jumbo or super jumbo is likely next in my collection.

You may also want to look at the guide regarding the tonality of certain woods and commit that to memory. The cost of some guitars could be in dressings that don't matter... such as gold dipped machine heads, or lots of inlays... and all that is fine as long as you've first found the best base guitar for yourself. Likely if you spend the same amount of money on a guitar that looks plain vs. a guitar that is all dressed up, you may find that the plain guitar is actualy better because it used to quality and properly aged woods.

Some other things that could affect sound is bone nut vs. plastic nuts... Kiln dried wood vs. naturally aged wood. Laminate backing vs. solid wood backing, even the type of joint that connects the neck to the guitar.

Most sales guys won't have all these answers for you..... so make 'em work for the sale and get the answers for you. They should have internet in the store and be able to look all this up for you.
2001 Gibson USA Les Paul Studio Black/Gold
2008 Alvarez-Yairi DY40C
2004 Taylor 310
Marshall AVT275

Ex guits 2002 Ovation Elite, 1995 Seagull 12 BC Rich Gunslinger Snakeskin Various Yamaha Various Sammick Epiphone Les Paul, Epiphone ES