Okay, I'm painting with a very very broad brush here so there's going to be exceptions both ways, but as a general rule of thumb then the following should see you right:
Stick with recognised Hi-Fi brands: Most of these are (or were originally) British companys: Monitor Audio, B&W, Rega, Focal (aka JM Labs), Mission, Wharfedale, Tannoy, Kef, Acoustic Energy, Dali, Castle, Ruark, Mission, Mordaunt Short, JPW, Celestion, Royd and you won't go far wrong.
On the whole, electronics manufacturers don't make or bring in decent speakers to the UK. That's because the UK is the world leader in manufacturing excellence for bookshelf Hi-Fi speakers (see above list). So, steer clear of Technics, Pioneer, Denon, Sony, Yamaha, Philips, Kenwood, JVC, Goodmans, Panasonic, Toshiba, Bush, LG, Samsung or anything that looks like it once belonged to one of those all-in-one DVD home cinema kits or a boombox stereo. There are some exceptions to the rule but unless you know what you are buying it's safer to go for the list at the top.
When Chinese manufacturing started to get popular there was a bit of a flood of cheaply-made speakers. These were the sort of thing sold by Richer Sounds and the other "pile-'em-high" discounters. Something small, British and decent like Wharfedale Diamonds might have cost you £90 new. The cheap Chinese alternatives might have cost you half that. But it's certainly true that you get what you pay for, so they weren't that great a bargain. Steer clear of Acoustic Solutions, Eltax, Gale, or anything with a name that sounds like a close relative of a bigger brand.
If the speakers you're looking at are any good then some magazine somewhere will have done a review. There's plenty of fish in this ocean.
As for a DAC; no. You don't need a DAC. The amp has one built in. Don't waste your money. BTW, the Lepai TA2020+ is an amplifier. It's not a DAC.