Hi Mikey ,
Yes, You can still run Lightroom 6 without using GPU.
Before you upgrade, I would highly recommend you to ensure that your computer meets all other system requirements.
Once Lighroom 6 is installed you can switch the GPU usage off following Adobe Lightroom GPU Troubleshooting and FAQ
You can run LR 6 as a trial, first. Download the LR 6 installer then the LR 6.5.1 patch from here, then install both:
Keep in mind that LR installs as LR CC until you register it with a LR 6 serial number, at which time you'll lose Dehaze, B/W Adjustment Brushes, Pano Boundary Warp, Guide Upright, which are LR CC only features until LR 7 if there will be a LR 7.
LR 6 is already up to LR 6.6 so it may not be too many more months before it is obsolete, so it may make more sense to sign up for LR CC at $120/year instead of LR 6 at $80, at least for the first year, then downgrade to LR 7 if there is a LR 7.
LR CC/6 will let me enable the GPU on my older 256MB video card on my older Windows 7 computer. It isn't necessarily better/faster, though, so while you may be able to enable the GPU it may not help, depending on how fast the GPU actually is compared to the CPU of your computer.