I acquired the h-bridge components elsewhere. Here's my parts order from digi-key for the microstepper.
My motors are rated for 2.0 Amps, so I used a set of 9.31K resistors for R2 and R8.
A pot is optional, but costs quite a bit. My costs are way down for this build.

1  	6  	P5305-ND  	CAP 1.0UF 100V ALUM LYTIC RADIAL  	C5,C2  	0  	0.18000  	$1.08
2 	6 	P5192-ND 	CAP 47UF 63V ALUM LYTIC RADIAL 	C4,C3 	0 	0.21000 	$1.26
3 	3 	P5309-ND 	CAP 10UF 100V ALUM LYTIC RADIAL 	C6 	0 	0.19000 	$0.57
4 	3 	ED1520-ND 	TERMINAL BLOCK 3.5MM 8POS PCB 	JP3 	0 	1.79000 	$5.37
5 	6 	ED1515-ND 	TERMINAL BLOCK 3.5MM 3POS PCB 	JP6,JP7 	0 	0.67000 	$4.02
6 	3 	490-1215-ND 	RESONATOR 20.0MHZ CERAMIC 	Y1 	0 	0.58000 	$1.74
7 	3 	ED1514-ND 	TERMINAL BLOCK 3.5MM 2POS PCB 	JP9 	0 	0.45000 	$1.35
8 	3 	296-1365-ND 	IC 5.0V 100MA REGULATOR TO-92 	U1 	0 	0.40000 	$1.20
9 	10 	1119PHCT-ND 	CAP 100V .0022UF AXIAL CERAM X7R 	C11,C1 	0 	0.08600 	$0.86
10 	3 	399-4151-ND 	CAP .1UF 50V 20% CER RADIAL 	C7 	0 	0.16000 	$0.48
11 	6 	399-4474-1-ND 	CAP 470PF 100V 10% CER AXIAL 	C12,C8 	0 	0.22000 	$1.32
12 	10 	20KQBK-ND 	RES 20K OHM 1/4W 5% CARBON FILM 	R7,R1 	0 	0.05400 	$0.54
13 	10 	6.65KXBK-ND 	RES 6.65K OHM 1/4W 1% METAL FILM 	R3 	0 	0.09800 	$0.98
14 	15 	10KQBK-ND 	RES 10K OHM 1/4W 5% CARBON FILM 	R4,R5,R6,R9 	0 	0.05400 	$0.81
15 	10 	9.31KXBK-ND 	RES 9.31K OHM 1/4W 1% METAL FILM 	R2,R8-2.0amp limiter 	0 	0.09800 	$0.98
16 	3 	PIC16F627A-I/P-ND 	IC MCU FLASH 1KX14 EEPROM 18DIP 	U3 	0 	2.95000 	$8.85

Extra bits

I got my heat sinks, DB-9 connectors and DB25 male to male cable from BGMicro.com.

4 heat sinks: $1.19 ea
4 DB9 female solder cup $.35 ea
4 DB9 male solder cup $.35 ea
4 DB9 hoods, $.35 ea
6 foot DB25 M-M cable $2.75