Start from where you are at, and keep going until you get where you need to go. We are all in a gradual process of upgrading our systems piece by piece, and doing so on limited budgets. So, certainly, amp now, speakers later.
But, give long consideration to what your needs are in the modern world of HiFi. Today, everything is moving to Digital Files. Today, many with a stereo are also using that stereo as the sound system for watching movies (raises hand). Many want to interface a computer with a good sound system for, among other things, Internet Radio.
While SACD hasn't really take off, if you tastes run beyond modern POP, then there is quite a selection out there to choose from.
If you haven't gone overboard on CD, and are still spinning stacks of hot wax (vinyl albums), then it is probably important to get an amp that can support a turntable.
Another aspects is Tone Controls or NO Tone Controls. I like having them, other don't feel they need them.
So, my point is, give some thought to what your Real Current needs are in an amp. Does the addition of an Internal DAC have any value for you? Are you more interested in High (more or less) power, or lower power but higher quality?
How do you feel about your previous NAD amp? (NAD ... right?) If you like NAD then the C356BEE or C356BEE-DAC are close to what you wanted to pay.
Another very worthy amp, is the XTZ A100 D3, but this is a beast of an amp, BIG and Powerful. Built-in DAC, Massive Power supply, Solid 110w/ch in Class A/B, and has pure Class A mode as well, no tone controls though. Price at a very reasonable £650, when you consider what you are getting.
XTZ Class A-100 D3 Integrated Stereo Amplifier Silver and Black | Integrated Amplifiers | Amplifiers | Audio Sanctum
Class A100 D3 Svart/Silver
It has ONE Optical and FOUR Coaxial, and no USB inputs feeding the internal DAC. Available in Black only, Silver only, and Black and Silver as shown. XTZ also makes some pretty impressive speakers.
Steve/bluewizard