some basics which would help everyone
a tv tuner basically comprises of a "ADC (broadcast decoder) + HF unit (broadcast receiver)
in addition some have hardware compressor MPEG-2 encoders as well
ADC mainly used are 9-bit PHILIPS SAA713x or 10-bit Conexant CX2388x
for hardware encoders Conexant CX258x + MPEG1 / 2 encoder Conexant CX23416-12.
though 12-bit ADC in ATI THEATER 650 is also there but unfortunately there is no PAL model for this currently
now naturally more the bits better the processing

hold on a minute
these ADC are standard chips. crappy local tuners too have SAA7134HL ADC & compro tv gold plus too has SAA7134HL ADC.
now why local tuners cost 600bucks & have crappy picture quality whereas videomate costs 3200bucks & has excellent picture quality

he he... answer is "receiver"
now local tuners have cheap receivers from crappy chinese firms whereas videomate tv gold plus 2 has original LG TPI8PSB12D HF unit.
secondly
Noise Removal starts at the level layout.capacitors & stabilizer located on the card have a great effect on overall picture quality and as a thumb rule local tuners lack such implementation
now for PAL good receivers are mainly from LG,Xceive,Huizhou TCL King High Frenquency Electronic Co & latest HF blocks from the Philips / NXP..
examples of some best tuners for PAL
compro videomate gold plus 2 :ADC Philips SAA7134HL+LG TPI8PSB12D
leadtek winfast tv 2000xp global: ADC CX23883-39 + Xceive XC2028
hauppage wintv PVR 150: ADC Conexant CX25843-23 + MPEG1 / 2 encoder Conexant CX23416-12 + HF unit Huizhou TCL MPE05
& latest compro M3 MCE and M5 MCE : philips SAA7131E + new generation of semiconductor receivers NXP
among all above receivers for PAL Huizhou TCL King High Frenquency Electronic Co & latest HF blocks from the Philips / NXP give better reception(though NXP based are not available right now)..
so best buy goes to hauppage wintv PVR 150(hardware encoder) then for software encoder is leadtek winfast tv 2000xp global