I'm a big fan of Dell, have bought dozens, desktops and a couple of servers, although for laptops I was always buying Thinkpads before I retired. The Intel Haswell processors and above are very impressive, as for Skylake, I can't see the advantage although support for DDR4 RAM is nice, don't know about costs though.
Unsolicited advice: I wouldn't do self-build, I can't see how it makes economic sense given the fantastic pricing from the likes of Dell. What I would always recommend though is clean-installing Windows properly from a straight retail _Microsoft_ Windows installation DVD, not an OEM one. I know it seems like a waste of money, but its for peace of mind, freedom from bloat and you can repair / recover your installation. And whatever you do, stay away from the Home versions of Windows as they are crippled and _impossible_ to secure, use Pro or whatever it's now called in Win 10. Then as long as you (i) don't _ever_ make it possible for anyone log on as an admin, and don't log on as an admin ever yourself unless it's for maintenance, (ii) set the whole NTFS FS with strict ACLs thoroughly, including locking down the root, (ask) and (iii) set up SRP thoroughly ultra-strictly (ask), (iv) use local Group Policy and lock in secured MS Office settings, and finally (v) lock the BIOS and make it only boot from C:, then you'll be fine. Problem apps that don't play nice on a secured o/s can be put into VMs. I did always stick with IE as it is definitely the most secure browser because of its use of o/s low-privilege 'integrity levels', and is securable by GP. For reliability, no dodgy device-drivers or kernel-mode third-party s/w, keep it minimal, lean and mean and especially don't go near third-party anti-virus / firewalls /anti-malware stick to MS' built-in offerings, so your o/s won’t run like a dog and crashing all the time. That's how I have never ever had crash or a security incident on any of my users' dozens or so machines in eight years - and no third-party a/v running at all. Users were not able to run exes that they downloaded from the web, received in email or imported on removable drives. Despite having non-computer literate users as well. I used such an ultra-secured setup for myself all the time too (we eat our own dog food). You didn't ask for that lot, and prob knew it all already, but I feel better now. Apologies.