Given a budget of $2500 for a new surround system (assuming you are starting from nothing), I would recommend the following...(Note: all pricing and recommendations are based on paying MSRP. If you can get the same/better quality for less then great, but I wanted to keep this simple)
The minimum I would spend on a 5.1 speaker setup (not including the receiver, speaker wire, cables, etc.) is $1200. An example of what you could get for this price point is the Definitive Technology ProCinema 800 set consisting of 4 small satellite/bookshelf speakers, a matched center channel, and subwoofer. Polk, Boston Acoustics, and Cambridge Audio have similar speaker packages around this same price point. If what you are looking for is primarily a good sounding, small home theatre system for watching movies and tv then this would be a good starting point. However, if you are planning on listening to a good amount of stereo music then I would suggest going with bigger front mains and a center channel that is matched to them. There isn't really a maximum that I would spend on the speakers, so that will be dictated by what is left after purchasing the receiver and accessories.
For the accessories (speaker wire, HDMI cables, speaker stands/mounts, etc.), I would expect to pay approx. $200. You might be able to do it for $100 if you already have enough HDMI cables and/or don't need stands/mounts for all of your speakers. Or, you might choose to spend as much as $300 on the accessories. With a total budget of $2500, I wouldn't spend more than that. For now, let's just use the $200 figure.
For the receiver, the minimum I would spend is $600. At this price point, your options for a new receiver include the: Denon AVR-E400, Sony STR-DN1040, and Yamaha RX-V675. These are at the upper end of these companies' "mid-tier" line of receivers, one step below there high end lines, have most of the features you might want, and are among the best in value. This is what I would call my bottom threshold. With a total budget of $2500, the max that I would spend on the receiver would again be influenced by the cost of the speakers and accessories.
Based on the minimum price of the speakers being $1200, the accessories costing approx. $200, and a minimum of $600 for the receiver, the current total price with tax would be around $2100. This leaves us with $400 of wiggle room. How you spend this extra $400 will depend on your answers to the questions I asked in my previous post.
You might choose to put it all towards the speakers, increasing your speaker budget to $1600. If your a music lover this might mean going with some larger bookshelves or even some cheaper/discounted floor standing speakers for your fronts (ie. Polk TSx330T, Klipsch Reference RF-42 II, etc.) and a matching center. If your main interest is movies and tv then you might bump up the size of all 6 speakers (5.1 channels) by the same amount.
You might choose to put it all towards the receiver, increasing your receiver budget to $1000. At this price point, you are into the high end lines (though not at the top of them). Options include the: Denon AVR-X3000, Marantz SR5000, NAD T 758, Onkyo TX-NR828, Pioneer Elite SC-71, Sony STR-DA2800ES, and Yamaha RX-A830.
Or, you might choose to split the extra $400 between the speakers and receiver which would put you at the entry level model for most receiver manufactures' high end line, while also giving you a couple hundred more to spend on speakers.