Hi
The NR 1605 is the step up version of NR 1604 and has all the gimmicks required in an AVR. Bluetooth, Wireless connectivity etc....it has 2 antennae for the same and there is no need to purchase the Rx 101 wireless device to be attached. however, the NR 1605 is 50w RMS @ 8 ohms per channel.
The SR 5008 is the audiophile designed series AVR which is 100w RMS @ 8 ohms. It is almost 7 inches in height (bulky).
Marantz is known for its quality products coupled with great performance and features. Although it may be cheaper in USA, you may want to consider carrying the weight all the way to India and also the customs factor if any.
Both these AVRs are around 13-14 inches deep, please check again on the website for accurate specs as you need to consider the speaker wiring connectors etc....
Marantz is available widely in India and some dealers would also offer the same as per USA rates, spare yourself the trouble of carrying the weight and facing customs, buy it locally.
There are many other AVRs like NAD, Cambridge Audio, Yamaha, Denon, etc. who have good products and most of them compete with each other in terms of features, prices etc. The key is for you to audition as many AVRs as possible and decide which one appeals to you in appearance, performance, features and cost. Make sure you take your kind of music and some movies along.
All the best.