The interesting thing with the Vortex is the field. It appears that it doesn't increase much with an 11mm increase in objective.
8x36 18 mm 16.4' 393' / 7.5° 4.9" 9.7 oz
8x25 15 mm 16.4' 378' / 7.2° 4.4" 5.6 oz
The Opticron 8x30 has a field of 428'. Confusing as it's more that the Votex that's 6mm bigger.
Which Opticron is that with 428' ?
http://www.opticron.co.uk/Pages/wp_mono.htm
Seems more like 390' or 131m 7.5 deg according to their website.
Unfortunately a lot of sites don't have the correct info and as for Amazon reviews, well....... never was such sheit "reviews" collected in one place. People on there love things like 18x21 bins or I think there are even worse ones they like such as 30x20 or something or the Sunagor 7x18 I bought recently based on all 5 star reviews and it was Sheit!
Ihe Specwell still looks reasonable to me but last evening I found my 8x20 to be not enjoyable at all really so now I would be concerned about the Specwell 8x30 but my 6x16 Specwells work fine in the sun so go figure. The sun really causes the 8x20 trouble and this happened also with the Opticron 8x20 gallery scope though I think that was slightly worse. To be honest if you can use that you can put up with anything.
I was looking again at my little Carson 7x18 MiniScout bin and I found it actually easier on my eyes than my Pentax 8x20 DCF ED (very similar to my RSPB HD 8x20) bin and I know I enjoy when out with the Carson and have problems when out with the Pentax even though the Pentax has Aspherical lenses and ED glass etc etc etc and costs many times more than the Carson but in the end the one that works is the best and for more distance my Carson 8x22 is also better than what should be a good compact in the Pentax.
Carson do a 10x25 Scout also for £34 on amazon. Forget the monoc and get one of those or the 8x22 if you want really light and compact.
Why must it be a monoc when it just won't be as good as small bins?
Here's a cheap 10x25 on here
http://www.birdforum.net/showthread.php?t=326600 He'd grab £60 I recon. I have one of these Hawke 10x25 and it's pretty decent as long as the sun doesn't bother it but it is water sealed and phase coated etc. Very light and compact but the Carson would probably beat it although not built as well as the Hawke.
Just occurred to me I could sell you these 8x20 Pentax if you like. Ok, bad idea
Keep searching.