Returning to DJing — DDJ-SR vs FLX4/FLX6 vs DDJ-800/1000 for UK Club Scene?

Hey everyone,
I’m a retired Serato DJ looking to get back into active gigging, mainly in clubs and pubs across the UK. A friend’s offering me his DDJ-SR for £400, but I’m also seeing FLX4 and FLX6 units going for around £350–£500 on Marketplace and eBay.

Here’s where I’m torn:

• I’m leaning toward learning Rekordbox to stay compatible with club setups and CDJs, but I’m worried about the limited connectivity on the FLX series (no balanced outs, no booth out).
• Would I be better off future-proofing with a DDJ-800 or DDJ-1000, if I can snag one in a distress sale?
• Do these higher-end units still hold up for 3–5 years of regular gigging, or are they starting to show their age?
• And realistically—how much of a limitation is RCA-only output in UK venues? Are there setups where this would be a dealbreaker?

I’d love to hear from DJs who’ve played out with these units or made the switch from Serato to Rekordbox. What would you go for if you were starting fresh today?

Thanks in advance!