Llanelli have been on a good recent run - consecutive wins have seen them move into third place in the Principality Premiership, and Buchanan acknowledges the need to progress further in the competition.
"I think the players are very aware of the importance of representing Wales in this competition," he said.
"We're the only team from the Principality Premiership in the quarter-finals and we've got to make sure we give it our all.
"It's all about winning and building that momentum. It's a fantastic tournament and it's great to test yourself against some of the best sides around.
"We haven't got past this round before, we've been to the quarter-finals but we're hoping to progress to the semis this time."
Llanelli have met Bedford on two previous occasions in the competition. In December 2011, the two sides shared a thrilling 25-25 draw while two years earlier, it was the Blues who edged a high scoring encounter 36-24.
Bedford have impressed in the competition so far, securing bonus point victories in all six of their pool games.
Buchanan added: "There is no doubting Bedford's ability and we know we've got to be at our best to beat them.
"We've played our best rugby in this competition and we're hoping that will continue on Saturday.
"We won't have too many opportunities but when we do, we'll have to take them. If we do that then we can cause a surprise."
Dan Thomas crossed for a hat-trick in Llanelli's last encounter, a high scoring win over Swansea. Llanelli field the majority of the same side that started at St. Helen's with Thomas partnering Lewis Rawlins and Craig Price in the back row tomorrow.
But after conceding four tries against the All Whites, Buchanan says his side's defence must improve.
"Dan Thomas is certainly a player to watch. There is no doubting his capabilities and they were certainly enhanced in the Six Nations recently with Wales Under 20," he said.
"But if we defend, scrummage and compete at the line-out like we did on Saturday then we will be under pressure."
Bedford are currently third in the English Championship and have combined their cup run with consistent league performances.
Blues Director of Rugby Mike Rayer is looking forward to the tie: "To have a good old fashioned knockout cup tie on a Saturday will be a huge boost for us," he said.
"We reached the final in this competition a couple of seasons ago and we'd love to do that again."
Bedford: 15 Ben Ransom 14 James Short 13 Brendan Burke 12 Mark Atkinson 11 Josh Bassett 10 Jake Sharp 9 Luke Baldwin, 1 Darren Fearn 2 Neil Cochrane 3 Ben Cooper 4 Mike Howard 5 Paul Tupai 6 Gregor Gillanders 7 Darren Fox (C) 8 Tom Armes.
Replacements: Scott Spurling, Dan Seal, Joe Vandermolen, Nick Fenton-Wells, Darryl Veenendaal, Myles Dorrian, Ollie Dodge.
Llanelli: 15 Dale Ford 14 Kristian Phillips 13 Nic Reynolds 12 Chris Keenan 11 Kyle Evans 10 Jonny Lewis 9 Gareth Davies, 1 Rhys Thomas 2 Kirby Myhill 3 Aled Hopkins 4 Adam Powell (C) 5 Joel Galley 6 Lewis Rawlins 7 Daniel Thomas 8 Craig Price.
Replacements: Jamie Kaijacks, Craig Hawkins, Craig Cross, Nathan White, Duane Eager, Justin James, Jordan Williams.