Valley's imperious form continued at Butlin Road, when they were on target four more times to brush aside their Northampton-based opponents.
Town raced to a three goal lead within the opening half an hour, before snatching a fourth late in the game to match the weekend's equally comfortable home victory over Newport Pagnell.
Dominic Perkins replaced Lee Thomas at left-back in the only change from the Pagnell success, but the first chance of the game fell to the visitors when Sam Watkins lifted a shot over the bar.
However Rugby were soon ahead in the fifth minute when Loyiso Recci powerfully headed home a Lewis Rankin corner - despite the best efforts of a Chenecks defender to clear it off the line.
Liam Francis then sent a further header over and Danico Johnson could also easily have doubled Town's advantage, before the diminutive Brandon Williams missed a great opportunity to level things up when he was clean through on goal - but he delayed his final shot and Valley keeper Matt Hill was able to save his angled effort.
The visitors were made to pay for this miss when Romario Martin scored a spectacular free-kick from distance - whipping it over the wall and past the bemused Jack Taylor into the net.
Taylor did then do well to keep out Richard Blythe's volley and Martin really should have finished off a long ball through the Northampton defence, but diverted the bouncing ball off-target as the hosts' early dominance continued.
A well-worked move produced Valley's third with Blythe's trickery feeding Johnson, who in-turn squared the ball across for Rankin to score into an empty net from close range.
With Johnson terrorising a by-now shaky-looking Chenecks back-line, he dragged one across the face of the goal and Blythe also lifted a shot wide of the frame.
The away side were still creating chances at the other end though, and Daniel Lumb had a shot saved by Hill after a mistake from Francis and Simeon Tulloch blocked Danny Quigley's header on the line.
Martin then cannoned one off the base of Taylor's post late in the first half, after a purposeful run by the Rugby forward.
The second period started quietly, and again it was Northampton who had the first real opportunity when Hill beat away another header from Quigley.
Valley eventually found their feet though and started to turn the screw on their opponents.
Johnson dragged the first of a number of dangerous deliveries from him across the face of the goal, whilst Taylor kept out quickfire efforts from first Johnson and then Charlie Evans after good assists from Daniel Kavanagh and Stefan Blake respectively.
A Martin free-kick missed the target this time and Francis headed wide, with Johnson also skewing his connection to Blake's cross, before Rugby's pressure finally paid dividends when Evans finished off another Johnson pull back to complete the scoring on 88 minutes.
Line-up: Hill; Kavanagh, Perkins, Recci, Francis; Hayden, Blythe, Rankin (Blake); Tulloch (Evans), Martin, Johnson. Subs not used: Edwards, Rosser, Steele. Booked: Hayden
Northampton line-up: Taylor, Ogden, Budd, Davis, Quigley, McDonald, Watkins, Nagy, Williams, Lumb, Spalding. Subs: Hunt, Green, Clayson, Sharpe, Tolworthy.