So what is your budget at the moment? A setup which can play music is also good for films IMO. Where do you live btw, that will determine what kind of equipment you can choose from. In the end it's al about going to the store and take a listen.
I like very 'bright'/transparent, aka neutral, speakers for instance. But a lot of people like B&W or whatever which have a lot of warmth. If you look at the frequency response of headphones you'll see that most people like to have a bit less volume around 4-8kHz(no harsh volcals, hissing 'S'). Supposingly people can't bear 'piercing treble' but choosing for a 'save' sound is also choosing for a boring sound IMO. This is al up to you. Some speakers however have a lot 15-20kHz to create an open sound. Like the paradigm monitors. This should be achieved with good phase behaviour, a lot of treble can be fatiqueing. They give a false impression and any bit of neutrallity is sacrificed in the process. I little extra highs isn't that bad though, my Elac's also have a little extra highs but due room acoustics this flattens out. They actually sound very dry.
Upgrading speakers will do a lot of good in your system I think. If you spend around 300euro per speaker you'll be able to buy something capable of getting some 'wow' factor. I was looking at 200/speaker but that won't get you mature/hifi sound in my experience. If I say capable I mean that there is more than just speakers to it. In your case I would keep the receiver for the moment, unless you have the money to upgrade both amp/speakers. A new amp alone won't give you an immediate upgrade because I think your speakers will really bottleneck. Which was your question in the first place. Different speakers ofcourse wil give a different sound right away. Don't under estimate amps though, a different amp might sound completely different. If you switch between my dad's naim amp and my marantz you might just think you are listening to some different speakers. The difference is that big. So upgrading your amp(to a stereo amp) would be the next step.
A system will sound only as good as the signal it plays so a investing in a good source after you've got the amp/speakers settled would not be a unlogical choice. The pro about your receiver is the DAC. it probably sounds better with the digital in than any amp directly feeded by a ipod. A ipod sounds very very bad. I've got the touch 4g and it's rediculous. The ultrasone hfi-2200 sounds like a piece of crap powered by it. Feeded by my cdp/amp it's al of a sudden an amazing piece of equipment. If you've got a tv with line-out that might be a sollution but now I am ahead of the situation.
A roomate of my brother has got a very expensive receiver (yamaha), more expensive than my amp, and he says it's crap. numbers don't say a lot but almost every receiver meassures very badly. My amp is 200euro's more expensive than your receiver and has 0,009%THD+N compared to 1%THD (no noise incalculated). A frequency response of 1,4Hz - 280kHz compaired to the 5Hz - 100kHz your reciever is capable of. Ofcourse harmonic distortion is not necessairly a bad thing and who cares about tones not within 20Hz-20kHz but It shows stereo amps are really made for sound reproduction. Where your receiver has almost twice the power, 70W compared to 130W, it seems like receiver is more focussed on showing of. 130W is rediculous because I can play music here louder than the average nightclub, average(loud) listening consumes about 1,5W. So a receiver is good on the wrong specs where a stereo amp is good in the important specs. This is why you should be very seriously consider going stereo instead of 5.1. My dad's naim amps however measure a lot worse as both of our amps and it sounds better than my amp by a long shot. This is why I said numbers don't say a lot, they are merely numbers. Go to the store and listen to some amps to find out what sounds good to you the moment you are ready to upgrade.
), ELAC's can't be overpowered. 