Here are some specs on which you can base your decision.
Onkyo 507
5 Channel Amp / 7.1 ch processing
DTS-HD Master Audio, DTS-HD High Resolution Audio, DTS-HD Express, Dolby TrueHD, Dolby Digital Plus Decoding
HDMI Version 1.3a to Support Deep Color, x.v.Color, LipSync, Dolby TrueHD, DTS-HD Master Audio, DVD-Audio, Super Audio CD, and CEC
HDTV-Capable HDMI Video Switching
Audyssey 2EQ to Correct Room Acoustic Problems
DTS-ES Discrete/Matrix, DTS Neo:6, DTS 96/24, Dolby Digital EX, Dolby Pro Logic IIx Decoding
DTS Surround Sensation Speaker Technology
H.C.P.S. (High Current Power Supply) Massive High Power Transformer
192 kHz/24-Bit DACs for All Channels
Advanced 32-Bit Processing DSP Chip
HDTV-Capable (720p/1080i) Component Video Switching (2 Inputs and 1 Output)
4 HDMI Inputs and 1 Output
4 Digital Inputs (2 Optical and 2 Coaxial)
4 A/V Inputs and 1 Output
1 Video Output (Monitor)
2 Audio Inputs and 1 Output
160 W/Ch at 6 Ohms, 1 kHz, 1 Channel Driven, JEITA
Frequency Response: 5 Hz-100 kHz (+1 dB, -3 dB)
Marantz 4003
7 ch Amp. / 7.1 ch Processing
ES/96/24/Discrete&Matrix6.1/Neo:6 DTS Support
Digital EX/Pro Logic IIx/Virtual Speaker/Headphone Dolby Support
192kHz/24-Bit D/A Conversion
Cirrus Logic 32-Bit DSP
S-Video to Component Video Up Conversion
3 HDMI In, 1 HDMI Out
3 Component In, 2 Out
5 (incl. Front) S-Video In, 2 Out
5 (incl. Front) Composite In, 2 Out
80W x7 (20Hz - 20kHz) Power Output (8 Ohm)
105dB S/N Ratio
8Hz - 100kHz (+/- 3 dB) Freq. Response (Analog In)
8Hz - 45kHz (+/- 3 dB) Freq. Response (Dig In)
Denon 1610
5 Channel Amp / 5.1 ch processing
All Dolby and DTS Processing.
DTS-HD Master Audio, DTS-HD High Resolution Audio, DTS-HD Express, Dolby TrueHD, Dolby Digital Plus Decoding
Audessey MultiEQ rooom correction and setup
Dolby Pro Logic IIz processing
3 HDMI In, 1 HDMI Out
2 Component In, 1 out
1 S-Video In, Zero Out
4 Composite In, 3 Out
3 Digital In (2 Optical, I Coax)
6 Analog In, 4 Out
75W x 5
98dB S/N Ratio
10Hz - 100kHz Freq. Response