I have recently got a set of yamaha 6.1 speakers as a present, but they need an amplifier to work (except for the sub i was told). So i've been searching on the internet on some entry level Receivers since i dont have very much money.

I was looking at

1) Denon 1801
2) Sony 495
3) Yamaha 430
4) Marantz 7300
5) Pioneer 512
6) Harman Kardon avr 130 (Harman kardon direct on Ebay about 200US)

I have no idea what the specifications mean, DTS, Dolby Digital but there are some many versions to them! Does anyone know what the difference is, i guess more is better, but are they brand specific? DTS ES, DTS EX, DTS Neo, i'm so confused, plus Dolby digital has like ES or EX too.....Also when it says 6.1 discrete input, does it mean it does have it or it can accept future upgrades to 6.1 (so 5.1 but will be able to support 6.1).

Does anyone know of any good and in-expensive amplifiers that they can recommend?
Any help or comments or opinions would be very helpful!