Well i've tried pushing mine as far as i can, 1240 on the core and 1500 on the memory but would probably do a little more on the memory front.
Not bad though for a REF 290X with the stock cooler!
Asus REF 290X @1240/1500
4770k @4.6
Sniper Elite V2 Benchmark Report
================================
Created: 2014-02-24 at 15:54:01
Build Version: 1.13, Apr 11 2013
================================
Average FPS: 56.0
Minimum FPS: 28.4
Maximum FPS: 295.9
Number Of Frames: 4294
Average Frame: 17.850ms
Minimum Frame: 3.379ms
Maximum Frame: 35.173ms
Machine Name: FIREHAWK
Monitors: 1
Operating System: Windows 8 (build 9200), 64-bit
System RAM: 8129MB
CPU: Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz
Number of Cores: 8
GPU Name: AMD Radeon R9 200 Series
Feature Level: DX11.0
Driver version: 8.17.10.1247
Dedicated VRAM: 3072MB
Resolution Width: 1920
Resolution Height: 1080
Texture Detail: ULTRA
Shadows Detail: ULTRA
Draw Distance: ULTRA
Anti-aliasing: HIGH
Advanced Shadows: HIGH
Supersampling: 4.0x
Anisotropic Level: 16
Compute Shaders: ON
Ambient Occlusion: ON
Motion Blur: ON
Vertical Sync: OFF
Reduce Mouse Lag: OFF
Stereo 3D: OFF
Could maybe get an extra frame out of it but would be difficult, happy with this though for now.